<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2021 Workiva-->
<!--r:868dbb86-7896-4cf8-8aea-a3f4655fef1e,g:badf5fbd-855c-47e7-9bb0-3a11157e0687-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://mmc.com/role/DocumentandEntityInformation" xlink:type="simple" xlink:href="mmc-20210331.xsd#DocumentandEntityInformation"/>
  <link:presentationLink xlink:role="http://mmc.com/role/DocumentandEntityInformation" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_CoverAbstract_00960bcc-b38f-4fc0-8497-944e99e47b2c" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_CoverAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_43cbd0cf-489c-43e4-a6d2-08e6c99b6182" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntitiesTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_00960bcc-b38f-4fc0-8497-944e99e47b2c" xlink:to="loc_dei_EntitiesTable_43cbd0cf-489c-43e4-a6d2-08e6c99b6182" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingsExchangeAxis_9ca2aa38-89f4-4801-8db9-e4463817f899" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityListingsExchangeAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntitiesTable_43cbd0cf-489c-43e4-a6d2-08e6c99b6182" xlink:to="loc_dei_EntityListingsExchangeAxis_9ca2aa38-89f4-4801-8db9-e4463817f899" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_ExchangeDomain_db56f41b-b9c8-47e4-b9db-90b8bfc2140b" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_ExchangeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityListingsExchangeAxis_9ca2aa38-89f4-4801-8db9-e4463817f899" xlink:to="loc_dei_ExchangeDomain_db56f41b-b9c8-47e4-b9db-90b8bfc2140b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_exch_XNYS_d3e2278c-e723-4b91-b96a-7abbb7a0afab" xlink:href="https://xbrl.sec.gov/exch/2020/exch-2020-01-31.xsd#exch_XNYS"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_ExchangeDomain_db56f41b-b9c8-47e4-b9db-90b8bfc2140b" xlink:to="loc_exch_XNYS_d3e2278c-e723-4b91-b96a-7abbb7a0afab" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_exch_XCHI_61362d1f-2e27-4b88-acae-49f8fe70f11a" xlink:href="https://xbrl.sec.gov/exch/2020/exch-2020-01-31.xsd#exch_XCHI"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_ExchangeDomain_db56f41b-b9c8-47e4-b9db-90b8bfc2140b" xlink:to="loc_exch_XCHI_61362d1f-2e27-4b88-acae-49f8fe70f11a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityInformationLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntitiesTable_43cbd0cf-489c-43e4-a6d2-08e6c99b6182" xlink:to="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_0edcb386-7b55-4410-ab31-5be31e93b221" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentType"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_DocumentType_0edcb386-7b55-4410-ab31-5be31e93b221" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_34e13ffc-fee6-4cc4-ae3d-888987320c74" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentQuarterlyReport"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_DocumentQuarterlyReport_34e13ffc-fee6-4cc4-ae3d-888987320c74" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_900829b4-be50-4e61-8fd5-02c5ffb81318" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentPeriodEndDate"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_DocumentPeriodEndDate_900829b4-be50-4e61-8fd5-02c5ffb81318" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_49ae0204-32f0-4ed1-8ce1-01f3aba0300a" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentTransitionReport"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_DocumentTransitionReport_49ae0204-32f0-4ed1-8ce1-01f3aba0300a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_be21469e-67bd-45ef-bdb9-68af9ae3cb7d" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityRegistrantName"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityRegistrantName_be21469e-67bd-45ef-bdb9-68af9ae3cb7d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_7fb3e9d1-6e96-4d69-bc41-7db7a09d3314" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityAddressAddressLine1"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityAddressAddressLine1_7fb3e9d1-6e96-4d69-bc41-7db7a09d3314" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_dfee03cd-073f-410e-abf7-be3b6de8bba0" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityAddressCityOrTown"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityAddressCityOrTown_dfee03cd-073f-410e-abf7-be3b6de8bba0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_c5d6f648-5e99-4aef-ad80-160ce0fc292a" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityAddressStateOrProvince"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityAddressStateOrProvince_c5d6f648-5e99-4aef-ad80-160ce0fc292a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_b14eb581-95b8-469e-a46c-23f92bdaff9d" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityAddressPostalZipCode"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityAddressPostalZipCode_b14eb581-95b8-469e-a46c-23f92bdaff9d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_3612a197-b91c-4975-85a7-8906cfea589e" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_CityAreaCode"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_CityAreaCode_3612a197-b91c-4975-85a7-8906cfea589e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_86d79570-f3af-4245-81e0-780af45e5458" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_LocalPhoneNumber"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_LocalPhoneNumber_86d79570-f3af-4245-81e0-780af45e5458" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_36b252e2-9f3e-4f94-8a0d-1b00922232bc" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityFileNumber"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityFileNumber_36b252e2-9f3e-4f94-8a0d-1b00922232bc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_90cb704b-22a2-4b62-b0c9-02ffb7ec4969" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:presentationArc order="13" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityIncorporationStateCountryCode_90cb704b-22a2-4b62-b0c9-02ffb7ec4969" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_4bfa982a-ad19-4f7f-a9f4-331a8c7c91b2" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:presentationArc order="14" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityTaxIdentificationNumber_4bfa982a-ad19-4f7f-a9f4-331a8c7c91b2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_c9caa680-a978-41ef-8efd-d50e64dfcdac" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_Security12bTitle"/>
    <link:presentationArc order="15" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_Security12bTitle_c9caa680-a978-41ef-8efd-d50e64dfcdac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_7396856a-f82b-463d-9fb8-5913151f9d67" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_TradingSymbol"/>
    <link:presentationArc order="16" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_TradingSymbol_7396856a-f82b-463d-9fb8-5913151f9d67" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_05e5605d-5bca-45f7-bd9e-b162b06889f6" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_SecurityExchangeName"/>
    <link:presentationArc order="17" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_SecurityExchangeName_05e5605d-5bca-45f7-bd9e-b162b06889f6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_f4de1361-271b-4e5e-8187-3d671928cc0c" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityCurrentReportingStatus"/>
    <link:presentationArc order="18" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityCurrentReportingStatus_f4de1361-271b-4e5e-8187-3d671928cc0c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_f10720d6-74ee-43e1-935e-01411608b4f9" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:presentationArc order="19" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityInteractiveDataCurrent_f10720d6-74ee-43e1-935e-01411608b4f9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_c88d2b25-cd07-4060-890d-bd7402eb89e1" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityFilerCategory"/>
    <link:presentationArc order="20" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityFilerCategory_c88d2b25-cd07-4060-890d-bd7402eb89e1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_b6c0b116-b57b-4f0a-a01b-afb85d93ccfd" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntitySmallBusiness"/>
    <link:presentationArc order="21" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntitySmallBusiness_b6c0b116-b57b-4f0a-a01b-afb85d93ccfd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_289c3a26-24a9-40f7-a753-12cff3221d53" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:presentationArc order="22" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityEmergingGrowthCompany_289c3a26-24a9-40f7-a753-12cff3221d53" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_df35e502-ecf1-4864-8c2f-60cb0f4b45ce" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityShellCompany"/>
    <link:presentationArc order="23" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityShellCompany_df35e502-ecf1-4864-8c2f-60cb0f4b45ce" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_11f6732a-5c32-4d65-996e-5688f5edbe92" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:presentationArc order="24" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_11f6732a-5c32-4d65-996e-5688f5edbe92" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_76be1b2a-9ec0-424f-9454-b4967b5c940a" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityCentralIndexKey"/>
    <link:presentationArc order="25" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_EntityCentralIndexKey_76be1b2a-9ec0-424f-9454-b4967b5c940a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_2e968356-e68a-4892-bdbd-3d42a8aa0934" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:presentationArc order="26" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_CurrentFiscalYearEndDate_2e968356-e68a-4892-bdbd-3d42a8aa0934" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_df4994cd-dc59-4191-bdde-e80eefd72acd" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentFiscalYearFocus"/>
    <link:presentationArc order="27" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_DocumentFiscalYearFocus_df4994cd-dc59-4191-bdde-e80eefd72acd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_109300b4-95e4-4307-9172-e61074665a01" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:presentationArc order="28" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_DocumentFiscalPeriodFocus_109300b4-95e4-4307-9172-e61074665a01" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_04dbf5fa-1677-4a9b-9585-171cae91b69b" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_AmendmentFlag"/>
    <link:presentationArc order="29" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityInformationLineItems_4f52e12e-fbd3-47b6-b119-2d9a809d9632" xlink:to="loc_dei_AmendmentFlag_04dbf5fa-1677-4a9b-9585-171cae91b69b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/ConsolidatedStatementsofIncomeUnaudited" xlink:type="simple" xlink:href="mmc-20210331.xsd#ConsolidatedStatementsofIncomeUnaudited"/>
  <link:presentationLink xlink:role="http://mmc.com/role/ConsolidatedStatementsofIncomeUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_14dc653f-2a60-4a34-8417-a4cddcb83162" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_14dc653f-2a60-4a34-8417-a4cddcb83162" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_177b4501-7c06-439f-add6-5f41c324b288" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_OperatingExpensesAbstract_177b4501-7c06-439f-add6-5f41c324b288" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_d46d7d95-464d-4b8a-9e74-fc3b0a231edc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OperatingExpensesAbstract_177b4501-7c06-439f-add6-5f41c324b288" xlink:to="loc_us-gaap_LaborAndRelatedExpense_d46d7d95-464d-4b8a-9e74-fc3b0a231edc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_424813d1-a321-40aa-8aa1-a3bb1bd0bb8b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OperatingExpensesAbstract_177b4501-7c06-439f-add6-5f41c324b288" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_424813d1-a321-40aa-8aa1-a3bb1bd0bb8b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_1f66b9da-3ff2-4838-8edb-bc112dd0b33c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpenses"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OperatingExpensesAbstract_177b4501-7c06-439f-add6-5f41c324b288" xlink:to="loc_us-gaap_OperatingExpenses_1f66b9da-3ff2-4838-8edb-bc112dd0b33c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_bec4ad83-a8bb-4edb-90dc-7806a646af6e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_OperatingIncomeLoss_bec4ad83-a8bb-4edb-90dc-7806a646af6e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanOtherCosts_9c1a9a0f-20bc-453a-b6bd-50ccc87d3a51" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanOtherCosts"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_DefinedBenefitPlanOtherCosts_9c1a9a0f-20bc-453a-b6bd-50ccc87d3a51" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_2926b7f6-f0c0-4f56-bc36-120a1e472aac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_InvestmentIncomeInterest_2926b7f6-f0c0-4f56-bc36-120a1e472aac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_828087a3-b84c-4d75-889e-4e2d85434a40" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestExpense"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_InterestExpense_828087a3-b84c-4d75-889e-4e2d85434a40" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnInvestments_02f31048-af31-4bb4-bafc-b0da46ff79da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnInvestments"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_GainLossOnInvestments_02f31048-af31-4bb4-bafc-b0da46ff79da" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_624ddc60-ee42-4c00-b5fd-23b6e6698afc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_624ddc60-ee42-4c00-b5fd-23b6e6698afc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_270273a8-7d81-4c59-84b4-79768e008b92" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_270273a8-7d81-4c59-84b4-79768e008b92" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_2de010b9-545b-429e-a03e-991ae0a0d3bd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_ProfitLoss_2de010b9-545b-429e-a03e-991ae0a0d3bd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_e9a3f3dd-a8d6-4e2c-bbf0-5af98c5ac4d4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_e9a3f3dd-a8d6-4e2c-bbf0-5af98c5ac4d4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_d4940a07-8226-468d-aa5b-cdc3be84be0c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_NetIncomeLoss_d4940a07-8226-468d-aa5b-cdc3be84be0c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_f0f6ae09-5962-411a-8fe7-8501603ee859" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract"/>
    <link:presentationArc order="13" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_f0f6ae09-5962-411a-8fe7-8501603ee859" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_d9af4d50-4da7-40a4-b7f0-0138f59ae930" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_f0f6ae09-5962-411a-8fe7-8501603ee859" xlink:to="loc_us-gaap_EarningsPerShareBasic_d9af4d50-4da7-40a4-b7f0-0138f59ae930" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_e0ca6216-815b-45b9-ae83-3acdbb457610" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareBasicAndDilutedAbstract_f0f6ae09-5962-411a-8fe7-8501603ee859" xlink:to="loc_us-gaap_EarningsPerShareDiluted_e0ca6216-815b-45b9-ae83-3acdbb457610" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_ca787736-d804-49fe-a028-aba52774ec38" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:presentationArc order="14" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_ca787736-d804-49fe-a028-aba52774ec38" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_0903cda3-f907-4cf4-8fb0-cc72c4f91bb2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_ca787736-d804-49fe-a028-aba52774ec38" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_0903cda3-f907-4cf4-8fb0-cc72c4f91bb2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_3365e0b9-1015-4b94-9caa-7dac11e9bb94" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_ca787736-d804-49fe-a028-aba52774ec38" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_3365e0b9-1015-4b94-9caa-7dac11e9bb94" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_42b8ea58-0633-4198-8584-f7ef48ffb13d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:presentationArc order="15" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementAbstract_93567bc9-5db6-4dd9-b1f0-678a220be036" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_42b8ea58-0633-4198-8584-f7ef48ffb13d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/ConsolidatedStatementsofComprehensiveIncomeUnaudited" xlink:type="simple" xlink:href="mmc-20210331.xsd#ConsolidatedStatementsofComprehensiveIncomeUnaudited"/>
  <link:presentationLink xlink:role="http://mmc.com/role/ConsolidatedStatementsofComprehensiveIncomeUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_6c78eb6b-a051-43e7-bf5a-463516800a1f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_911a04b7-a766-4f32-8920-5083fefd4a03" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_6c78eb6b-a051-43e7-bf5a-463516800a1f" xlink:to="loc_us-gaap_ProfitLoss_911a04b7-a766-4f32-8920-5083fefd4a03" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPeriodIncreaseDecreaseAbstract_d3a0de93-d3da-4eac-8e28-ef804ae96ec2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTaxPeriodIncreaseDecreaseAbstract"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_6c78eb6b-a051-43e7-bf5a-463516800a1f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPeriodIncreaseDecreaseAbstract_d3a0de93-d3da-4eac-8e28-ef804ae96ec2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax_00aeac59-70b6-44c3-85a8-9dedd77be116" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPeriodIncreaseDecreaseAbstract_d3a0de93-d3da-4eac-8e28-ef804ae96ec2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax_00aeac59-70b6-44c3-85a8-9dedd77be116" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_cdf459fc-34e1-4cde-bb61-507912974ac7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPeriodIncreaseDecreaseAbstract_d3a0de93-d3da-4eac-8e28-ef804ae96ec2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_cdf459fc-34e1-4cde-bb61-507912974ac7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_1cbc205b-eedc-440e-a56b-d5a36e2f64e0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTax"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPeriodIncreaseDecreaseAbstract_d3a0de93-d3da-4eac-8e28-ef804ae96ec2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_1cbc205b-eedc-440e-a56b-d5a36e2f64e0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_2b5e21c6-b481-45a5-820b-58550512ece6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossTax"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_6c78eb6b-a051-43e7-bf5a-463516800a1f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_2b5e21c6-b481-45a5-820b-58550512ece6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_757aa9a0-08f1-41a8-b01b-6b9820eb95c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_6c78eb6b-a051-43e7-bf5a-463516800a1f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_757aa9a0-08f1-41a8-b01b-6b9820eb95c5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_22428818-37b2-4835-af8e-9cecc6fafcb8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_6c78eb6b-a051-43e7-bf5a-463516800a1f" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_22428818-37b2-4835-af8e-9cecc6fafcb8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_e1ad7d29-4348-4bd7-89e7-3635d5ad05d8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_6c78eb6b-a051-43e7-bf5a-463516800a1f" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_e1ad7d29-4348-4bd7-89e7-3635d5ad05d8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_1923c7bd-f91b-48c8-b264-cace59a04e90" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_6c78eb6b-a051-43e7-bf5a-463516800a1f" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_1923c7bd-f91b-48c8-b264-cace59a04e90" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="mmc-20210331.xsd#ConsolidatedBalanceSheets"/>
  <link:presentationLink xlink:role="http://mmc.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfFinancialPositionAbstract_e844618a-a84f-4ed5-915d-d0f6fa1095d6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfFinancialPositionAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsAbstract"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_e844618a-a84f-4ed5-915d-d0f6fa1095d6" xlink:to="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_3a9705ea-4b20-431e-8974-3c50d4f86274" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:to="loc_us-gaap_AssetsCurrentAbstract_3a9705ea-4b20-431e-8974-3c50d4f86274" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_a6242497-e68d-432b-8d7a-7a5326d546fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3a9705ea-4b20-431e-8974-3c50d4f86274" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_a6242497-e68d-432b-8d7a-7a5326d546fc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesNetCurrentAbstract_c12146f3-514e-4084-b17f-fb2219980502" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReceivablesNetCurrentAbstract"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3a9705ea-4b20-431e-8974-3c50d4f86274" xlink:to="loc_us-gaap_ReceivablesNetCurrentAbstract_c12146f3-514e-4084-b17f-fb2219980502" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_AccruedFeesandOtherRevenueReceivableGrossCurrent_057db048-28db-4b70-b0a7-1f62bd352d9a" xlink:href="mmc-20210331.xsd#mmc_AccruedFeesandOtherRevenueReceivableGrossCurrent"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ReceivablesNetCurrentAbstract_c12146f3-514e-4084-b17f-fb2219980502" xlink:to="loc_mmc_AccruedFeesandOtherRevenueReceivableGrossCurrent_057db048-28db-4b70-b0a7-1f62bd352d9a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_AdvancedPremiumsandClaimsReceivableGrossCurrent_d779f9d5-d0a4-4f6a-b403-3ad12385a681" xlink:href="mmc-20210331.xsd#mmc_AdvancedPremiumsandClaimsReceivableGrossCurrent"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ReceivablesNetCurrentAbstract_c12146f3-514e-4084-b17f-fb2219980502" xlink:to="loc_mmc_AdvancedPremiumsandClaimsReceivableGrossCurrent_d779f9d5-d0a4-4f6a-b403-3ad12385a681" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivablesGrossCurrent_8de9ce7d-8e99-41be-be11-1cdb9d6cc592" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherReceivablesGrossCurrent"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ReceivablesNetCurrentAbstract_c12146f3-514e-4084-b17f-fb2219980502" xlink:to="loc_us-gaap_OtherReceivablesGrossCurrent_8de9ce7d-8e99-41be-be11-1cdb9d6cc592" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableGrossCurrent_bee2e59d-08fe-4d34-a13e-71aa9ed249d8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsReceivableGrossCurrent"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ReceivablesNetCurrentAbstract_c12146f3-514e-4084-b17f-fb2219980502" xlink:to="loc_us-gaap_AccountsReceivableGrossCurrent_bee2e59d-08fe-4d34-a13e-71aa9ed249d8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_e3347f6c-6cf3-47e6-a2ac-1349104adaea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ReceivablesNetCurrentAbstract_c12146f3-514e-4084-b17f-fb2219980502" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_e3347f6c-6cf3-47e6-a2ac-1349104adaea" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesNetCurrent_809dc7b2-32c5-4e7a-a75c-f651cc28c78b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReceivablesNetCurrent"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ReceivablesNetCurrentAbstract_c12146f3-514e-4084-b17f-fb2219980502" xlink:to="loc_us-gaap_ReceivablesNetCurrent_809dc7b2-32c5-4e7a-a75c-f651cc28c78b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_0a77cd98-a4f3-41d4-9b48-8a45881d0e7e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3a9705ea-4b20-431e-8974-3c50d4f86274" xlink:to="loc_us-gaap_OtherAssetsCurrent_0a77cd98-a4f3-41d4-9b48-8a45881d0e7e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_f83a6b5e-8f97-42f3-b319-98e504de1dec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsCurrent"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsCurrentAbstract_3a9705ea-4b20-431e-8974-3c50d4f86274" xlink:to="loc_us-gaap_AssetsCurrent_f83a6b5e-8f97-42f3-b319-98e504de1dec" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_1f256bc6-9386-486c-a246-f2ef8ca6063e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:to="loc_us-gaap_Goodwill_1f256bc6-9386-486c-a246-f2ef8ca6063e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsNet_ad25eeef-d642-4a06-b55f-9879e70e199b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIntangibleAssetsNet"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:to="loc_us-gaap_OtherIntangibleAssetsNet_ad25eeef-d642-4a06-b55f-9879e70e199b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_40683cf1-c800-4721-a204-a2cc12d3a784" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_40683cf1-c800-4721-a204-a2cc12d3a784" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_3339eca9-59d3-463d-945d-65e9d25fcaef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:to="loc_us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_3339eca9-59d3-463d-945d-65e9d25fcaef" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_904415c8-b305-454d-9a83-653c5e7f9f94" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_904415c8-b305-454d-9a83-653c5e7f9f94" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_342566b5-00d6-4053-819e-48bd711d0df0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_342566b5-00d6-4053-819e-48bd711d0df0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_4df39902-5d56-4ece-bda7-9bb444916da0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_4df39902-5d56-4ece-bda7-9bb444916da0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_bca7e282-8c65-46bf-aa91-f5c215b4b792" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsAbstract_1c16f060-d6c7-458e-bb5d-a77aa45ebc08" xlink:to="loc_us-gaap_Assets_bca7e282-8c65-46bf-aa91-f5c215b4b792" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_e844618a-a84f-4ed5-915d-d0f6fa1095d6" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_fb9155c6-aee4-4b2f-82e2-55c7b7a385fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_fb9155c6-aee4-4b2f-82e2-55c7b7a385fe" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_6683bda6-e46c-4fd1-9adf-55b985f9396d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtCurrent"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fb9155c6-aee4-4b2f-82e2-55c7b7a385fe" xlink:to="loc_us-gaap_DebtCurrent_6683bda6-e46c-4fd1-9adf-55b985f9396d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_5074c3d3-a956-429f-bea7-94135a12e818" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fb9155c6-aee4-4b2f-82e2-55c7b7a385fe" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_5074c3d3-a956-429f-bea7-94135a12e818" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_b4cf70ed-3b10-46e9-bcc6-91eaf5093712" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fb9155c6-aee4-4b2f-82e2-55c7b7a385fe" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_b4cf70ed-3b10-46e9-bcc6-91eaf5093712" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_0489cbc0-ab97-4d87-a6b4-5a5dfecb877e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fb9155c6-aee4-4b2f-82e2-55c7b7a385fe" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_0489cbc0-ab97-4d87-a6b4-5a5dfecb877e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesCurrent_06c56bfc-2d18-42ed-894c-577fd25cf8c8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedIncomeTaxesCurrent"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fb9155c6-aee4-4b2f-82e2-55c7b7a385fe" xlink:to="loc_us-gaap_AccruedIncomeTaxesCurrent_06c56bfc-2d18-42ed-894c-577fd25cf8c8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableCurrent_ffec4c99-6fe0-4cd4-8b5d-b58c9a9728c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DividendsPayableCurrent"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fb9155c6-aee4-4b2f-82e2-55c7b7a385fe" xlink:to="loc_us-gaap_DividendsPayableCurrent_ffec4c99-6fe0-4cd4-8b5d-b58c9a9728c5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_82596187-24ff-47e5-9a64-92d326f9b7f4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fb9155c6-aee4-4b2f-82e2-55c7b7a385fe" xlink:to="loc_us-gaap_LiabilitiesCurrent_82596187-24ff-47e5-9a64-92d326f9b7f4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiduciaryLiabilitiesGrossNoncurrent_d28735ee-aa61-4484-b808-5404f2c61f3e" xlink:href="mmc-20210331.xsd#mmc_FiduciaryLiabilitiesGrossNoncurrent"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_mmc_FiduciaryLiabilitiesGrossNoncurrent_d28735ee-aa61-4484-b808-5404f2c61f3e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_CashandInvestmentsHeldinFiduciaryCapacityNoncurrent_31cf7236-2511-4c32-9c65-4097e53f3071" xlink:href="mmc-20210331.xsd#mmc_CashandInvestmentsHeldinFiduciaryCapacityNoncurrent"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_mmc_CashandInvestmentsHeldinFiduciaryCapacityNoncurrent_31cf7236-2511-4c32-9c65-4097e53f3071" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiduciaryLiabilitiesNetNoncurrent_94233af3-ae91-49ba-8b31-fd9addd0031f" xlink:href="mmc-20210331.xsd#mmc_FiduciaryLiabilitiesNetNoncurrent"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_mmc_FiduciaryLiabilitiesNetNoncurrent_94233af3-ae91-49ba-8b31-fd9addd0031f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_288d1112-7ca2-43b3-8149-6b2f435896be" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_288d1112-7ca2-43b3-8149-6b2f435896be" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent_0a92c644-c038-42e2-b65e-9edf30569924" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent_0a92c644-c038-42e2-b65e-9edf30569924" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_9362657c-37d6-4370-a317-e99231562072" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_9362657c-37d6-4370-a317-e99231562072" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_LiabilityForErrorsAndOmissions_fa964361-2c76-421b-bae8-8a3114ae2e14" xlink:href="mmc-20210331.xsd#mmc_LiabilityForErrorsAndOmissions"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_mmc_LiabilityForErrorsAndOmissions_fa964361-2c76-421b-bae8-8a3114ae2e14" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_7e6bbfad-f514-4898-8b11-cd2203046343" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_7e6bbfad-f514-4898-8b11-cd2203046343" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_bcf38033-f893-4a60-acf5-a0c47864a979" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_us-gaap_CommitmentsAndContingencies_bcf38033-f893-4a60-acf5-a0c47864a979" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_ec5d8571-018f-49ce-97b2-9f2ea0ba45f4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockValue"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:to="loc_us-gaap_PreferredStockValue_ec5d8571-018f-49ce-97b2-9f2ea0ba45f4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_2c434872-b460-41a9-ba6c-a0272f8788fb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockValue"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:to="loc_us-gaap_CommonStockValue_2c434872-b460-41a9-ba6c-a0272f8788fb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_d9f72d7c-ec56-4709-b7d0-5aeea5ac3522" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_d9f72d7c-ec56-4709-b7d0-5aeea5ac3522" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_5ff8987e-3c43-4330-bbcc-0893fba89fde" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_5ff8987e-3c43-4330-bbcc-0893fba89fde" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_7f4cd1b9-2e8c-484d-94ac-cb0a7a9f34b5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_7f4cd1b9-2e8c-484d-94ac-cb0a7a9f34b5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_fbe0f052-64b9-438c-b4fb-1cd86b942b0d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MinorityInterest"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:to="loc_us-gaap_MinorityInterest_fbe0f052-64b9-438c-b4fb-1cd86b942b0d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_StockholdersEquitySubtotalBeforeTreasuryStock_8be4fa88-2eb6-491b-b616-bdebe523dd7b" xlink:href="mmc-20210331.xsd#mmc_StockholdersEquitySubtotalBeforeTreasuryStock"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:to="loc_mmc_StockholdersEquitySubtotalBeforeTreasuryStock_8be4fa88-2eb6-491b-b616-bdebe523dd7b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_e219cd6b-3425-4965-8f74-9f723279a475" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValue"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:to="loc_us-gaap_TreasuryStockValue_e219cd6b-3425-4965-8f74-9f723279a475" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_b001bb0a-3738-48f7-a075-2b11d23a6a5e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_0fb685e5-56c2-46e3-85f9-e59ca5a665d9" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_b001bb0a-3738-48f7-a075-2b11d23a6a5e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_195bee45-e07e-4830-a268-463da322c5da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_b9e02d37-12a4-4f4d-be81-c6a3e5f99669" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_195bee45-e07e-4830-a268-463da322c5da" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" xlink:href="mmc-20210331.xsd#ConsolidatedBalanceSheetsParenthetical"/>
  <link:presentationLink xlink:role="http://mmc.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfFinancialPositionAbstract_3cbd4be6-066d-44ae-a87b-c6889c6b1572" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfFinancialPositionAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_a5925f15-9eb8-498c-ac87-cd21305a6663" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_3cbd4be6-066d-44ae-a87b-c6889c6b1572" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_a5925f15-9eb8-498c-ac87-cd21305a6663" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_17100296-6256-4794-bc5d-11dc4e8db3e2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_3cbd4be6-066d-44ae-a87b-c6889c6b1572" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_17100296-6256-4794-bc5d-11dc4e8db3e2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_970b8b0f-4379-4e9b-a24a-57877a8180d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_3cbd4be6-066d-44ae-a87b-c6889c6b1572" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_970b8b0f-4379-4e9b-a24a-57877a8180d2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_e0f61c60-8672-4d43-8d42-99a57c497eb4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_3cbd4be6-066d-44ae-a87b-c6889c6b1572" xlink:to="loc_us-gaap_PreferredStockSharesIssued_e0f61c60-8672-4d43-8d42-99a57c497eb4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_368a4cd0-3c53-4699-b364-447ec849f37a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_3cbd4be6-066d-44ae-a87b-c6889c6b1572" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_368a4cd0-3c53-4699-b364-447ec849f37a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_0d283767-48a9-4bc1-bbe3-23933839522c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_3cbd4be6-066d-44ae-a87b-c6889c6b1572" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_0d283767-48a9-4bc1-bbe3-23933839522c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_ca69d5f0-b533-42b9-a03d-6f8c36b41036" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_3cbd4be6-066d-44ae-a87b-c6889c6b1572" xlink:to="loc_us-gaap_CommonStockSharesIssued_ca69d5f0-b533-42b9-a03d-6f8c36b41036" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockShares_0ddaccbc-2424-44f3-b85a-2841393c8d41" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockShares"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_3cbd4be6-066d-44ae-a87b-c6889c6b1572" xlink:to="loc_us-gaap_TreasuryStockShares_0ddaccbc-2424-44f3-b85a-2841393c8d41" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/ConsolidatedStatementsofCashFlowsUnaudited" xlink:type="simple" xlink:href="mmc-20210331.xsd#ConsolidatedStatementsofCashFlowsUnaudited"/>
  <link:presentationLink xlink:role="http://mmc.com/role/ConsolidatedStatementsofCashFlowsUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfCashFlowsAbstract_1abcf54a-ef8d-403e-b9f2-cb58256dfadf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfCashFlowsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b5029ae1-1190-426b-a931-9d07706dce12" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract_1abcf54a-ef8d-403e-b9f2-cb58256dfadf" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b5029ae1-1190-426b-a931-9d07706dce12" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_b4b8cdf1-2bab-4bc7-b597-6305efc932c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b5029ae1-1190-426b-a931-9d07706dce12" xlink:to="loc_us-gaap_ProfitLoss_b4b8cdf1-2bab-4bc7-b597-6305efc932c5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b5029ae1-1190-426b-a931-9d07706dce12" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_b6b56e9b-78d2-488a-a2cc-521a445ff6e6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Depreciation"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:to="loc_us-gaap_Depreciation_b6b56e9b-78d2-488a-a2cc-521a445ff6e6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_0d331706-f775-41a0-af06-7823db377139" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_0d331706-f775-41a0-af06-7823db377139" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_LeasesRightOfUseAssetAmortization_0cfa93d4-27e6-457a-a0cb-7457f5256543" xlink:href="mmc-20210331.xsd#mmc_LeasesRightOfUseAssetAmortization"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:to="loc_mmc_LeasesRightOfUseAssetAmortization_0cfa93d4-27e6-457a-a0cb-7457f5256543" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_5134d738-f859-4b71-a436-6dbd27fffce6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_5134d738-f859-4b71-a436-6dbd27fffce6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_ba82be15-526f-4e64-a8ed-c9212552a397" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_ba82be15-526f-4e64-a8ed-c9212552a397" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnInvestments_82b15e8f-8dfb-4961-b457-bfd66c3555c8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnInvestments"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:to="loc_us-gaap_GainLossOnInvestments_82b15e8f-8dfb-4961-b457-bfd66c3555c8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfOtherAssets_33552cee-a82a-4ef1-a609-5841aed0dbe5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnSaleOfOtherAssets"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:to="loc_us-gaap_GainLossOnSaleOfOtherAssets_33552cee-a82a-4ef1-a609-5841aed0dbe5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_e53ba0b0-5c44-4297-bcd9-737c03c7eac7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:to="loc_us-gaap_ShareBasedCompensation_e53ba0b0-5c44-4297-bcd9-737c03c7eac7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_c313e298-701a-45ef-b8cb-c9d5078bd599" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInReceivables_90ae82da-41d9-4a7c-9334-1decc02e32f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInReceivables"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_us-gaap_IncreaseDecreaseInReceivables_90ae82da-41d9-4a7c-9334-1decc02e32f9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_59101952-bb1a-4452-bb4c-f406f704e84f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherCurrentAssets"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_59101952-bb1a-4452-bb4c-f406f704e84f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_30ab83b9-3b22-48c5-a566-53ece982c2de" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentAssets"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_30ab83b9-3b22-48c5-a566-53ece982c2de" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_340f7fda-4f69-4488-8b0f-019d7c566389" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_340f7fda-4f69-4488-8b0f-019d7c566389" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_48c569d4-d3c4-4884-ba42-16eb1bf2a7a8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_48c569d4-d3c4-4884-ba42-16eb1bf2a7a8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_c13b201e-8657-4786-8177-924449bfc576" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable_c13b201e-8657-4786-8177-924449bfc576" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense_1df209f8-556e-444e-8942-90cc7154347f" xlink:href="mmc-20210331.xsd#mmc_PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_mmc_PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense_1df209f8-556e-444e-8942-90cc7154347f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_7ce9f9bb-ee1a-4637-8ff0-b197bf9ff743" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_7ce9f9bb-ee1a-4637-8ff0-b197bf9ff743" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_IncreaseDecreaseinOperatingLeaseLiabilities_fbceadb8-4cfc-4064-a362-72001f9c898b" xlink:href="mmc-20210331.xsd#mmc_IncreaseDecreaseinOperatingLeaseLiabilities"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_mmc_IncreaseDecreaseinOperatingLeaseLiabilities_fbceadb8-4cfc-4064-a362-72001f9c898b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_EffectofExchangeRateonCashandCashEquivalentsfromOperatingActivities_2389815f-b7f7-4628-b73c-54afa8b50427" xlink:href="mmc-20210331.xsd#mmc_EffectofExchangeRateonCashandCashEquivalentsfromOperatingActivities"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_331731f1-96b4-4309-8457-c0f4a986e322" xlink:to="loc_mmc_EffectofExchangeRateonCashandCashEquivalentsfromOperatingActivities_2389815f-b7f7-4628-b73c-54afa8b50427" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_4be44d2a-24ad-4b9a-a8b7-0ad22662ae92" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_b5029ae1-1190-426b-a931-9d07706dce12" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_4be44d2a-24ad-4b9a-a8b7-0ad22662ae92" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract_1abcf54a-ef8d-403e-b9f2-cb58256dfadf" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_40758018-c669-43a3-a836-456364935bab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_40758018-c669-43a3-a836-456364935bab" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromRepaymentsOfCommercialPaper_fbd98b46-4cd0-46c5-bb4c-9867201ff989" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromRepaymentsOfCommercialPaper"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_ProceedsFromRepaymentsOfCommercialPaper_fbd98b46-4cd0-46c5-bb4c-9867201ff989" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_e6a4647b-6460-47bd-9c73-9bf4cbf92fce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_e6a4647b-6460-47bd-9c73-9bf4cbf92fce" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_9374ebcd-c24d-436e-acae-da3c638e1b0c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_9374ebcd-c24d-436e-acae-da3c638e1b0c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries_1f4aea4a-4de7-4448-9bf4-d4e059e86cd0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries_1f4aea4a-4de7-4448-9bf4-d4e059e86cd0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_7988fd0c-aa54-4a82-a337-e56419fcb0dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_7988fd0c-aa54-4a82-a337-e56419fcb0dc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_7fe784b4-d8a2-4d57-a6c3-c5d28053554e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_7fe784b4-d8a2-4d57-a6c3-c5d28053554e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PaymentsforAcquisitionsDeferredandContingentConsideration_6d666395-5676-425b-b546-f4fb25b5aceb" xlink:href="mmc-20210331.xsd#mmc_PaymentsforAcquisitionsDeferredandContingentConsideration"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_mmc_PaymentsforAcquisitionsDeferredandContingentConsideration_6d666395-5676-425b-b546-f4fb25b5aceb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToMinorityShareholders_8d8d210c-0852-4266-ac6b-0a7712cb74ef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToMinorityShareholders"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_PaymentsToMinorityShareholders_8d8d210c-0852-4266-ac6b-0a7712cb74ef" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividendsCommonStock_1d1d12c1-44c9-447d-bf4b-42ce8520c656" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsOfDividendsCommonStock"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_PaymentsOfDividendsCommonStock_1d1d12c1-44c9-447d-bf4b-42ce8520c656" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_b833db02-f0ea-4bb8-91e7-13f57c852582" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_28941e13-33ac-42bd-ba5f-d1d57a6acc53" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_b833db02-f0ea-4bb8-91e7-13f57c852582" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_8fba3167-b86d-4ab1-89c1-45e8bec1c299" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract_1abcf54a-ef8d-403e-b9f2-cb58256dfadf" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_8fba3167-b86d-4ab1-89c1-45e8bec1c299" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_f6111441-7543-49e0-a762-0ff8c77ce62c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_8fba3167-b86d-4ab1-89c1-45e8bec1c299" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_f6111441-7543-49e0-a762-0ff8c77ce62c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromInvestments_22c2e7cc-1170-42ff-811d-7b9d25b58f13" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForProceedsFromInvestments"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_8fba3167-b86d-4ab1-89c1-45e8bec1c299" xlink:to="loc_us-gaap_PaymentsForProceedsFromInvestments_22c2e7cc-1170-42ff-811d-7b9d25b58f13" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates_e1bbf4b2-7906-4980-ae6d-88f086af3df4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_8fba3167-b86d-4ab1-89c1-45e8bec1c299" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinessesAndInterestsInAffiliates_e1bbf4b2-7906-4980-ae6d-88f086af3df4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_d8eed6e4-2ad7-41e0-9dd1-fd3badf26921" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_8fba3167-b86d-4ab1-89c1-45e8bec1c299" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_d8eed6e4-2ad7-41e0-9dd1-fd3badf26921" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_505e8f7f-5474-46e1-8cae-ab1e0fe8e2f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_8fba3167-b86d-4ab1-89c1-45e8bec1c299" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_505e8f7f-5474-46e1-8cae-ab1e0fe8e2f9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_5a886ba8-830a-4790-8f57-b85e4e29a379" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_8fba3167-b86d-4ab1-89c1-45e8bec1c299" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_5a886ba8-830a-4790-8f57-b85e4e29a379" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_55d68b39-39e4-474a-9147-b26dfd04fbe6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract_1abcf54a-ef8d-403e-b9f2-cb58256dfadf" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_55d68b39-39e4-474a-9147-b26dfd04fbe6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_d738836f-a4ad-46e2-b803-2ce68ce80f0b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract_1abcf54a-ef8d-403e-b9f2-cb58256dfadf" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_d738836f-a4ad-46e2-b803-2ce68ce80f0b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_1e6bbada-2d21-4926-b6aa-c4c9f9c8fc3a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract_1abcf54a-ef8d-403e-b9f2-cb58256dfadf" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_1e6bbada-2d21-4926-b6aa-c4c9f9c8fc3a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_679f4b77-2082-4ab0-bc84-6ef5e441b913" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfCashFlowsAbstract_1abcf54a-ef8d-403e-b9f2-cb58256dfadf" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_679f4b77-2082-4ab0-bc84-6ef5e441b913" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/ConsolidatedStatementsofEquityUnaudited" xlink:type="simple" xlink:href="mmc-20210331.xsd#ConsolidatedStatementsofEquityUnaudited"/>
  <link:presentationLink xlink:role="http://mmc.com/role/ConsolidatedStatementsofEquityUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfStockholdersEquityAbstract_10cb57cc-aa71-4eba-9000-878a2d014ce3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfStockholdersEquityAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_bc9584e2-2b69-446b-a0ac-9e53d1d785d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementOfStockholdersEquityAbstract_10cb57cc-aa71-4eba-9000-878a2d014ce3" xlink:to="loc_us-gaap_StatementTable_bc9584e2-2b69-446b-a0ac-9e53d1d785d7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_e64bb16c-6168-4107-b4c0-5f04b5de08a5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementTable_bc9584e2-2b69-446b-a0ac-9e53d1d785d7" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_e64bb16c-6168-4107-b4c0-5f04b5de08a5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_9c9fdaea-3aaf-4cbd-adf2-aec2820e045a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_e64bb16c-6168-4107-b4c0-5f04b5de08a5" xlink:to="loc_us-gaap_EquityComponentDomain_9c9fdaea-3aaf-4cbd-adf2-aec2820e045a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_5fd041b6-7794-4758-a69c-9a3482428c2c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityComponentDomain_9c9fdaea-3aaf-4cbd-adf2-aec2820e045a" xlink:to="loc_us-gaap_CommonStockMember_5fd041b6-7794-4758-a69c-9a3482428c2c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_22736906-b1d8-493b-aed0-b5532bd2a204" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityComponentDomain_9c9fdaea-3aaf-4cbd-adf2-aec2820e045a" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_22736906-b1d8-493b-aed0-b5532bd2a204" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_8e9654c0-106f-4973-81ff-c02bb3dfff4a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityComponentDomain_9c9fdaea-3aaf-4cbd-adf2-aec2820e045a" xlink:to="loc_us-gaap_RetainedEarningsMember_8e9654c0-106f-4973-81ff-c02bb3dfff4a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b298b1cf-df59-47dd-8441-de0b6ab2ba32" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityComponentDomain_9c9fdaea-3aaf-4cbd-adf2-aec2820e045a" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b298b1cf-df59-47dd-8441-de0b6ab2ba32" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockMember_35dc3a16-bace-49cd-908f-c8cd5e2d32fe" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockMember"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityComponentDomain_9c9fdaea-3aaf-4cbd-adf2-aec2820e045a" xlink:to="loc_us-gaap_TreasuryStockMember_35dc3a16-bace-49cd-908f-c8cd5e2d32fe" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_16a497b5-48fd-421f-8cc1-904d90ef3841" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityComponentDomain_9c9fdaea-3aaf-4cbd-adf2-aec2820e045a" xlink:to="loc_us-gaap_NoncontrollingInterestMember_16a497b5-48fd-421f-8cc1-904d90ef3841" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_d6c9909d-fda6-406f-9770-f7d41f40f89a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementTable_bc9584e2-2b69-446b-a0ac-9e53d1d785d7" xlink:to="loc_us-gaap_StatementLineItems_d6c9909d-fda6-406f-9770-f7d41f40f89a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementLineItems_d6c9909d-fda6-406f-9770-f7d41f40f89a" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_24299ca5-bd8a-46e1-b2bf-05de51625025" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_24299ca5-bd8a-46e1-b2bf-05de51625025" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_05ebba72-7315-4f75-9bba-aa42fff0a68d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_05ebba72-7315-4f75-9bba-aa42fff0a68d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_StockIssuedDuringPeriodValueSharebasedCompensationandEmployeeStockPurchasePlanAndRelatedTaxDeficiency_c360aee0-60b9-43ef-ab9d-162de60ff459" xlink:href="mmc-20210331.xsd#mmc_StockIssuedDuringPeriodValueSharebasedCompensationandEmployeeStockPurchasePlanAndRelatedTaxDeficiency"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_mmc_StockIssuedDuringPeriodValueSharebasedCompensationandEmployeeStockPurchasePlanAndRelatedTaxDeficiency_c360aee0-60b9-43ef-ab9d-162de60ff459" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_5a03c997-94bd-4733-ab11-13b394b9264f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalOther"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_5a03c997-94bd-4733-ab11-13b394b9264f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_b36ab1b6-6c97-44b6-955a-83d63d042e74" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_ProfitLoss_b36ab1b6-6c97-44b6-955a-83d63d042e74" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsShareBasedCompensationCash_abbf39bc-2980-42fa-9683-e35f1c00eba8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DividendsShareBasedCompensationCash"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_DividendsShareBasedCompensationCash_abbf39bc-2980-42fa-9683-e35f1c00eba8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_69a2dfe9-9695-41c6-aaa4-732323c6724f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_DividendsCommonStockCash_69a2dfe9-9695-41c6-aaa4-732323c6724f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_d4ea2954-d43b-40d5-b5d7-7fb6e21c5549" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_d4ea2954-d43b-40d5-b5d7-7fb6e21c5549" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_75d227d0-cfa1-4f7b-8ab4-692495ac37df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_75d227d0-cfa1-4f7b-8ab4-692495ac37df" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestIncreaseFromBusinessCombination_88071d3c-4779-4494-8bbc-da6e8450028d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NoncontrollingInterestIncreaseFromBusinessCombination"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_NoncontrollingInterestIncreaseFromBusinessCombination_88071d3c-4779-4494-8bbc-da6e8450028d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_9c520f2c-4c8b-447b-bce2-7616abfe370f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_9c520f2c-4c8b-447b-bce2-7616abfe370f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_b6e16f51-7077-4f03-b3ff-eacc4081d9dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bfb6a18e-ed3a-4fcc-a72c-e571cb80ef77" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_b6e16f51-7077-4f03-b3ff-eacc4081d9dc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_CommonStockDividendsPerShareCashDeclared_e8325e53-5c44-4ecd-a9d5-ffcd3abdda0d" xlink:href="mmc-20210331.xsd#mmc_CommonStockDividendsPerShareCashDeclared"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementLineItems_d6c9909d-fda6-406f-9770-f7d41f40f89a" xlink:to="loc_mmc_CommonStockDividendsPerShareCashDeclared_e8325e53-5c44-4ecd-a9d5-ffcd3abdda0d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/NatureofOperations" xlink:type="simple" xlink:href="mmc-20210331.xsd#NatureofOperations"/>
  <link:presentationLink xlink:role="http://mmc.com/role/NatureofOperations" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_13facc97-2bce-4fd0-865d-41212c7bce52" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NatureOfOperations_fb45aa16-46f5-421f-bc2f-aa66aef9c6f6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NatureOfOperations"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_13facc97-2bce-4fd0-865d-41212c7bce52" xlink:to="loc_us-gaap_NatureOfOperations_fb45aa16-46f5-421f-bc2f-aa66aef9c6f6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/NatureofOperationsDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#NatureofOperationsDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/NatureofOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_656fccf7-9bfe-4bf8-933c-7443f702c55d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfOperatingSegments_40997af4-63d4-4310-81dc-52b29cd39251" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NumberOfOperatingSegments"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_656fccf7-9bfe-4bf8-933c-7443f702c55d" xlink:to="loc_us-gaap_NumberOfOperatingSegments_40997af4-63d4-4310-81dc-52b29cd39251" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PercentageOfOpenOffices_2ab928cb-e08f-46f3-bf3b-e9ba273ccb1f" xlink:href="mmc-20210331.xsd#mmc_PercentageOfOpenOffices"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_656fccf7-9bfe-4bf8-933c-7443f702c55d" xlink:to="loc_mmc_PercentageOfOpenOffices_2ab928cb-e08f-46f3-bf3b-e9ba273ccb1f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/PrinciplesofConsolidationandOtherMatters" xlink:type="simple" xlink:href="mmc-20210331.xsd#PrinciplesofConsolidationandOtherMatters"/>
  <link:presentationLink xlink:role="http://mmc.com/role/PrinciplesofConsolidationandOtherMatters" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_c4e0be97-731b-4a8c-ab2e-84c9dce6226a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock_f6c27fec-be23-41d0-a6a4-4fa5b4a9baeb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_c4e0be97-731b-4a8c-ab2e-84c9dce6226a" xlink:to="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureAndSignificantAccountingPoliciesTextBlock_f6c27fec-be23-41d0-a6a4-4fa5b4a9baeb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/PrinciplesofConsolidationandOtherMattersPolicies" xlink:type="simple" xlink:href="mmc-20210331.xsd#PrinciplesofConsolidationandOtherMattersPolicies"/>
  <link:presentationLink xlink:role="http://mmc.com/role/PrinciplesofConsolidationandOtherMattersPolicies" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_73784612-b422-4b59-aab7-bfc753f493c7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsPolicyTextBlock_e556ca3f-8be6-4b37-bf70-29cfaa4504eb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsPolicyTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_73784612-b422-4b59-aab7-bfc753f493c7" xlink:to="loc_us-gaap_CashAndCashEquivalentsPolicyTextBlock_e556ca3f-8be6-4b37-bf70-29cfaa4504eb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditLossFinancialInstrumentPolicyTextBlock_d6a2bb75-4d59-4b49-af75-9ed07f120add" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditLossFinancialInstrumentPolicyTextBlock"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_73784612-b422-4b59-aab7-bfc753f493c7" xlink:to="loc_us-gaap_CreditLossFinancialInstrumentPolicyTextBlock_d6a2bb75-4d59-4b49-af75-9ed07f120add" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentPolicyTextBlock_9398ab22-a294-40c9-a331-fd35cf3363d1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentPolicyTextBlock"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_73784612-b422-4b59-aab7-bfc753f493c7" xlink:to="loc_us-gaap_InvestmentPolicyTextBlock_9398ab22-a294-40c9-a331-fd35cf3363d1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxPolicyTextBlock_71b11d3f-375f-44fa-88fb-cdcd73ed0f8b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxPolicyTextBlock"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_73784612-b422-4b59-aab7-bfc753f493c7" xlink:to="loc_us-gaap_IncomeTaxPolicyTextBlock_71b11d3f-375f-44fa-88fb-cdcd73ed0f8b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAssociatedWithExitOrDisposalActivitiesOrRestructuringsPolicyTextBlock_a5ce9fef-9a49-4ba2-9009-9bc863634dc0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostsAssociatedWithExitOrDisposalActivitiesOrRestructuringsPolicyTextBlock"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_73784612-b422-4b59-aab7-bfc753f493c7" xlink:to="loc_us-gaap_CostsAssociatedWithExitOrDisposalActivitiesOrRestructuringsPolicyTextBlock_a5ce9fef-9a49-4ba2-9009-9bc863634dc0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementPolicyPolicyTextBlock_9396ab40-5ad4-422a-93eb-77eb1d55cc53" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementPolicyPolicyTextBlock"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_73784612-b422-4b59-aab7-bfc753f493c7" xlink:to="loc_us-gaap_FairValueMeasurementPolicyPolicyTextBlock_9396ab40-5ad4-422a-93eb-77eb1d55cc53" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_398526ee-3718-4e60-bd46-cbe3879f81ce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_73784612-b422-4b59-aab7-bfc753f493c7" xlink:to="loc_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_398526ee-3718-4e60-bd46-cbe3879f81ce" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/PrinciplesofConsolidationAndOtherMattersDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#PrinciplesofConsolidationAndOtherMattersDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/PrinciplesofConsolidationAndOtherMattersDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_7c12d8b6-330c-4ae7-b724-f120d851cfad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleTable_c9c70f05-44ce-49dd-8c86-f3327bec3017" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_7c12d8b6-330c-4ae7-b724-f120d851cfad" xlink:to="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleTable_c9c70f05-44ce-49dd-8c86-f3327bec3017" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_82695597-dde6-46ed-a290-4cef9f2e1295" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleTable_c9c70f05-44ce-49dd-8c86-f3327bec3017" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_82695597-dde6-46ed-a290-4cef9f2e1295" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_9d016054-8bed-4917-ad61-0d5ba85c5b68" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_82695597-dde6-46ed-a290-4cef9f2e1295" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_9d016054-8bed-4917-ad61-0d5ba85c5b68" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_AlexanderForbesGroupHoldingsLimitedMember_341c7ef7-c7be-46dc-a2ee-a8f3119f6de7" xlink:href="mmc-20210331.xsd#mmc_AlexanderForbesGroupHoldingsLimitedMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_9d016054-8bed-4917-ad61-0d5ba85c5b68" xlink:to="loc_mmc_AlexanderForbesGroupHoldingsLimitedMember_341c7ef7-c7be-46dc-a2ee-a8f3119f6de7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_065bda96-30f5-493c-9db5-37d44c9a8c41" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleTable_c9c70f05-44ce-49dd-8c86-f3327bec3017" xlink:to="loc_us-gaap_InvestmentTypeAxis_065bda96-30f5-493c-9db5-37d44c9a8c41" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_d7d10e57-ab32-436c-8c2a-cff75caa8c2b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_InvestmentTypeAxis_065bda96-30f5-493c-9db5-37d44c9a8c41" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_d7d10e57-ab32-436c-8c2a-cff75caa8c2b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrivateEquityFundsMember_71e8dc31-9aa7-4825-8fdd-b23324284a8e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrivateEquityFundsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_d7d10e57-ab32-436c-8c2a-cff75caa8c2b" xlink:to="loc_us-gaap_PrivateEquityFundsMember_71e8dc31-9aa7-4825-8fdd-b23324284a8e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_2806ef04-1de3-4a6f-ad4e-d2c1d4932266" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleTable_c9c70f05-44ce-49dd-8c86-f3327bec3017" xlink:to="loc_srt_RangeAxis_2806ef04-1de3-4a6f-ad4e-d2c1d4932266" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_60675fb4-e167-4d8c-979a-a7e82586628b" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeAxis_2806ef04-1de3-4a6f-ad4e-d2c1d4932266" xlink:to="loc_srt_RangeMember_60675fb4-e167-4d8c-979a-a7e82586628b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_3f1d33a1-c404-4a7e-baf7-1206d19a7ff0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeMember_60675fb4-e167-4d8c-979a-a7e82586628b" xlink:to="loc_srt_MinimumMember_3f1d33a1-c404-4a7e-baf7-1206d19a7ff0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_d9271ca8-a5f2-4320-9ce6-f1df9b952fc4" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeMember_60675fb4-e167-4d8c-979a-a7e82586628b" xlink:to="loc_srt_MaximumMember_d9271ca8-a5f2-4320-9ce6-f1df9b952fc4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems_f2571ec2-3d23-4b9c-a120-8eb1c7bd4fb9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleTable_c9c70f05-44ce-49dd-8c86-f3327bec3017" xlink:to="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems_f2571ec2-3d23-4b9c-a120-8eb1c7bd4fb9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_f586771f-b601-441b-99ca-0436abb45320" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems_f2571ec2-3d23-4b9c-a120-8eb1c7bd4fb9" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_f586771f-b601-441b-99ca-0436abb45320" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_EquityMethodInvestmentLagPeriod_3bf65347-2e11-4b51-8b07-6861b2e09994" xlink:href="mmc-20210331.xsd#mmc_EquityMethodInvestmentLagPeriod"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems_f2571ec2-3d23-4b9c-a120-8eb1c7bd4fb9" xlink:to="loc_mmc_EquityMethodInvestmentLagPeriod_3bf65347-2e11-4b51-8b07-6861b2e09994" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnInvestments_58e3a866-22af-4e08-bc3d-b1660e76a117" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GainLossOnInvestments"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems_f2571ec2-3d23-4b9c-a120-8eb1c7bd4fb9" xlink:to="loc_us-gaap_GainLossOnInvestments_58e3a866-22af-4e08-bc3d-b1660e76a117" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_d4b4ebda-7938-4559-8ad1-c98189a729ff" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems_f2571ec2-3d23-4b9c-a120-8eb1c7bd4fb9" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_d4b4ebda-7938-4559-8ad1-c98189a729ff" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitPercent_63d2b338-2c7f-46f7-9149-544aa7041bbc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitPercent"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems_f2571ec2-3d23-4b9c-a120-8eb1c7bd4fb9" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitPercent_63d2b338-2c7f-46f7-9149-544aa7041bbc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_e1b83901-f80f-4caa-8d06-6c0b295a2266" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_UnrecognizedTaxBenefits"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems_f2571ec2-3d23-4b9c-a120-8eb1c7bd4fb9" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_e1b83901-f80f-4caa-8d06-6c0b295a2266" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible_3a225cd3-fc53-4963-80c8-636e449d0694" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems_f2571ec2-3d23-4b9c-a120-8eb1c7bd4fb9" xlink:to="loc_us-gaap_DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible_3a225cd3-fc53-4963-80c8-636e449d0694" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/Revenue" xlink:type="simple" xlink:href="mmc-20210331.xsd#Revenue"/>
  <link:presentationLink xlink:role="http://mmc.com/role/Revenue" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerAbstract_3e53f51c-0406-4719-aab5-e5179b4939e8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerTextBlock_586a0f55-4a4c-4ad4-a27a-aed7851b88f3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerAbstract_3e53f51c-0406-4719-aab5-e5179b4939e8" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerTextBlock_586a0f55-4a4c-4ad4-a27a-aed7851b88f3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RevenueTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#RevenueTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RevenueTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerAbstract_46d766ab-d43c-459e-bcd1-766bad535b45" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTableTextBlock_d0106ad5-8864-4a26-bb13-68700e381f9b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueTableTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerAbstract_46d766ab-d43c-459e-bcd1-766bad535b45" xlink:to="loc_us-gaap_DisaggregationOfRevenueTableTextBlock_d0106ad5-8864-4a26-bb13-68700e381f9b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetAndLiabilityTableTextBlock_1cd03f56-d861-4fa6-b3b3-7f11b4020a17" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerAssetAndLiabilityTableTextBlock"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerAbstract_46d766ab-d43c-459e-bcd1-766bad535b45" xlink:to="loc_us-gaap_ContractWithCustomerAssetAndLiabilityTableTextBlock_1cd03f56-d861-4fa6-b3b3-7f11b4020a17" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RevenueDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RevenueDisaggregationofRevenueDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RevenueDisaggregationofRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerAbstract_4bbe3fdc-db6f-4b72-92c6-651f875a44fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_64322ed1-b1fd-4de5-895d-8d3daca0f741" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerAbstract_4bbe3fdc-db6f-4b72-92c6-651f875a44fd" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_64322ed1-b1fd-4de5-895d-8d3daca0f741" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsAxis_b46078ee-1873-4719-8d71-706f7235d98f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsegmentsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_64322ed1-b1fd-4de5-895d-8d3daca0f741" xlink:to="loc_us-gaap_SubsegmentsAxis_b46078ee-1873-4719-8d71-706f7235d98f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsDomain_d7c17583-a1cd-46a4-8e40-cc7c3c8aaa9a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsegmentsDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsAxis_b46078ee-1873-4719-8d71-706f7235d98f" xlink:to="loc_us-gaap_SubsegmentsDomain_d7c17583-a1cd-46a4-8e40-cc7c3c8aaa9a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_MarshGuyCarpenterMember_0eeec5a2-6449-4f6f-8ed7-b681585b8969" xlink:href="mmc-20210331.xsd#mmc_MarshGuyCarpenterMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_d7c17583-a1cd-46a4-8e40-cc7c3c8aaa9a" xlink:to="loc_mmc_MarshGuyCarpenterMember_0eeec5a2-6449-4f6f-8ed7-b681585b8969" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_MarshInsuranceGroupMember_f63dc309-e317-4872-bda3-cc7b8bd80041" xlink:href="mmc-20210331.xsd#mmc_MarshInsuranceGroupMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_MarshGuyCarpenterMember_0eeec5a2-6449-4f6f-8ed7-b681585b8969" xlink:to="loc_mmc_MarshInsuranceGroupMember_f63dc309-e317-4872-bda3-cc7b8bd80041" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_GuyCarpenterReinsuranceGroupMember_ac34620b-8928-44b8-babd-4c475188cb2f" xlink:href="mmc-20210331.xsd#mmc_GuyCarpenterReinsuranceGroupMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_MarshGuyCarpenterMember_0eeec5a2-6449-4f6f-8ed7-b681585b8969" xlink:to="loc_mmc_GuyCarpenterReinsuranceGroupMember_ac34620b-8928-44b8-babd-4c475188cb2f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_MercerConsultingGroupMember_785884e7-5f37-43d2-95af-e3f6750627ef" xlink:href="mmc-20210331.xsd#mmc_MercerConsultingGroupMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_d7c17583-a1cd-46a4-8e40-cc7c3c8aaa9a" xlink:to="loc_mmc_MercerConsultingGroupMember_785884e7-5f37-43d2-95af-e3f6750627ef" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OliverWymanGroupConsultingGroupMember_b79e452b-eb5a-4bb0-bb67-d441a3858f71" xlink:href="mmc-20210331.xsd#mmc_OliverWymanGroupConsultingGroupMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_d7c17583-a1cd-46a4-8e40-cc7c3c8aaa9a" xlink:to="loc_mmc_OliverWymanGroupConsultingGroupMember_b79e452b-eb5a-4bb0-bb67-d441a3858f71" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_b0aeeb8e-cda6-4387-8c8c-6c6daa774128" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_64322ed1-b1fd-4de5-895d-8d3daca0f741" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_b0aeeb8e-cda6-4387-8c8c-6c6daa774128" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_84bc5412-b6d7-41f6-951a-83b169a3b8cd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_b0aeeb8e-cda6-4387-8c8c-6c6daa774128" xlink:to="loc_us-gaap_SegmentDomain_84bc5412-b6d7-41f6-951a-83b169a3b8cd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_RiskandInsuranceServicesSegmentMember_0e90c3c6-d861-4494-ac66-ba34a47af4d1" xlink:href="mmc-20210331.xsd#mmc_RiskandInsuranceServicesSegmentMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_84bc5412-b6d7-41f6-951a-83b169a3b8cd" xlink:to="loc_mmc_RiskandInsuranceServicesSegmentMember_0e90c3c6-d861-4494-ac66-ba34a47af4d1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_ConsultingSegmentMember_ca0615c1-22e1-4bd5-9b96-38448e040070" xlink:href="mmc-20210331.xsd#mmc_ConsultingSegmentMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_84bc5412-b6d7-41f6-951a-83b169a3b8cd" xlink:to="loc_mmc_ConsultingSegmentMember_ca0615c1-22e1-4bd5-9b96-38448e040070" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_76743e5d-19c4-4a48-9d3b-4bc2841f3714" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_64322ed1-b1fd-4de5-895d-8d3daca0f741" xlink:to="loc_srt_StatementGeographicalAxis_76743e5d-19c4-4a48-9d3b-4bc2841f3714" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_42747418-3887-40fd-bdfa-3a5240e3a2ef" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_StatementGeographicalAxis_76743e5d-19c4-4a48-9d3b-4bc2841f3714" xlink:to="loc_srt_SegmentGeographicalDomain_42747418-3887-40fd-bdfa-3a5240e3a2ef" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_InternationalMember_ff37945a-75b6-4c79-9c91-6de174fe9f43" xlink:href="mmc-20210331.xsd#mmc_InternationalMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_SegmentGeographicalDomain_42747418-3887-40fd-bdfa-3a5240e3a2ef" xlink:to="loc_mmc_InternationalMember_ff37945a-75b6-4c79-9c91-6de174fe9f43" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_a4374071-6ec3-492f-b48e-5ff655d1189f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EMEAMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_InternationalMember_ff37945a-75b6-4c79-9c91-6de174fe9f43" xlink:to="loc_us-gaap_EMEAMember_a4374071-6ec3-492f-b48e-5ff655d1189f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_03848715-e59c-46a0-8bc7-7d15cb60f089" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_AsiaPacificMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_InternationalMember_ff37945a-75b6-4c79-9c91-6de174fe9f43" xlink:to="loc_srt_AsiaPacificMember_03848715-e59c-46a0-8bc7-7d15cb60f089" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LatinAmericaMember_e51a1308-3def-440e-bee8-ab73780521d8" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_LatinAmericaMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_InternationalMember_ff37945a-75b6-4c79-9c91-6de174fe9f43" xlink:to="loc_srt_LatinAmericaMember_e51a1308-3def-440e-bee8-ab73780521d8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_UnitedStatesandCanadaMember_f28fa9a3-92eb-41bf-a56c-30e1de03a7e5" xlink:href="mmc-20210331.xsd#mmc_UnitedStatesandCanadaMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_SegmentGeographicalDomain_42747418-3887-40fd-bdfa-3a5240e3a2ef" xlink:to="loc_mmc_UnitedStatesandCanadaMember_f28fa9a3-92eb-41bf-a56c-30e1de03a7e5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_4bad62ec-2020-41c1-bb2b-33edc131aff1" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_64322ed1-b1fd-4de5-895d-8d3daca0f741" xlink:to="loc_srt_ProductOrServiceAxis_4bad62ec-2020-41c1-bb2b-33edc131aff1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_69ec2e8c-f33b-409c-b051-d74048628f70" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ProductOrServiceAxis_4bad62ec-2020-41c1-bb2b-33edc131aff1" xlink:to="loc_srt_ProductsAndServicesDomain_69ec2e8c-f33b-409c-b051-d74048628f70" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_WealthMember_30317c2c-4023-43e4-a0cc-5688ff512050" xlink:href="mmc-20210331.xsd#mmc_WealthMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ProductsAndServicesDomain_69ec2e8c-f33b-409c-b051-d74048628f70" xlink:to="loc_mmc_WealthMember_30317c2c-4023-43e4-a0cc-5688ff512050" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_HealthMember_dcf00bda-6dd7-4567-ab32-4483d8419ddd" xlink:href="mmc-20210331.xsd#mmc_HealthMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ProductsAndServicesDomain_69ec2e8c-f33b-409c-b051-d74048628f70" xlink:to="loc_mmc_HealthMember_dcf00bda-6dd7-4567-ab32-4483d8419ddd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_CareerMember_cd55bd73-2123-4239-bdba-86edb2c609e3" xlink:href="mmc-20210331.xsd#mmc_CareerMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ProductsAndServicesDomain_69ec2e8c-f33b-409c-b051-d74048628f70" xlink:to="loc_mmc_CareerMember_cd55bd73-2123-4239-bdba-86edb2c609e3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_d3bb524e-3069-4a8d-ac07-f9f668d766ca" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_64322ed1-b1fd-4de5-895d-8d3daca0f741" xlink:to="loc_us-gaap_DisaggregationOfRevenueLineItems_d3bb524e-3069-4a8d-ac07-f9f668d766ca" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_cb6cb2d7-52c0-47ee-a60a-064d5f9be26b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d3bb524e-3069-4a8d-ac07-f9f668d766ca" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_cb6cb2d7-52c0-47ee-a60a-064d5f9be26b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_InterestIncomeFiduciaryAssets_750e3080-46c1-4733-b9ee-35f13b8ed699" xlink:href="mmc-20210331.xsd#mmc_InterestIncomeFiduciaryAssets"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d3bb524e-3069-4a8d-ac07-f9f668d766ca" xlink:to="loc_mmc_InterestIncomeFiduciaryAssets_750e3080-46c1-4733-b9ee-35f13b8ed699" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RevenueContractAssetsandContractLiabilitiesDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RevenueContractAssetsandContractLiabilitiesDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RevenueContractAssetsandContractLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerAbstract_47ba161c-f967-4084-a5bf-785ddfe6935b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNet_1c6394d2-9136-42f0-b679-6e13a4413079" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerAssetNet"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerAbstract_47ba161c-f967-4084-a5bf-785ddfe6935b" xlink:to="loc_us-gaap_ContractWithCustomerAssetNet_1c6394d2-9136-42f0-b679-6e13a4413079" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_84ecb319-f4ea-4f44-83a2-6bbd8731fd14" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerAbstract_47ba161c-f967-4084-a5bf-785ddfe6935b" xlink:to="loc_us-gaap_ContractWithCustomerLiability_84ecb319-f4ea-4f44-83a2-6bbd8731fd14" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RevenueNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RevenueNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RevenueNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerAbstract_fcdce4b7-0d8a-4015-8c43-35e03fd59835" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_2ab1e754-5cf1-4c1f-af1f-e045bcca8df9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerAbstract_fcdce4b7-0d8a-4015-8c43-35e03fd59835" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_2ab1e754-5cf1-4c1f-af1f-e045bcca8df9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsAxis_59fe9ffb-492b-4280-81a2-1a0da9377e5c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsegmentsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2ab1e754-5cf1-4c1f-af1f-e045bcca8df9" xlink:to="loc_us-gaap_SubsegmentsAxis_59fe9ffb-492b-4280-81a2-1a0da9377e5c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsDomain_15c4c5bb-bc4d-41ca-831c-41bfb4c43966" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsegmentsDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsAxis_59fe9ffb-492b-4280-81a2-1a0da9377e5c" xlink:to="loc_us-gaap_SubsegmentsDomain_15c4c5bb-bc4d-41ca-831c-41bfb4c43966" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_MarshInsuranceGroupMember_2b88785f-faaf-457e-a714-19fdec64b2f1" xlink:href="mmc-20210331.xsd#mmc_MarshInsuranceGroupMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_15c4c5bb-bc4d-41ca-831c-41bfb4c43966" xlink:to="loc_mmc_MarshInsuranceGroupMember_2b88785f-faaf-457e-a714-19fdec64b2f1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_MercerConsultingGroupMember_786e0b23-a89f-4808-9dcc-80921b8d3c9d" xlink:href="mmc-20210331.xsd#mmc_MercerConsultingGroupMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_15c4c5bb-bc4d-41ca-831c-41bfb4c43966" xlink:to="loc_mmc_MercerConsultingGroupMember_786e0b23-a89f-4808-9dcc-80921b8d3c9d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OliverWymanGroupConsultingGroupMember_6b57950b-7a9e-4643-9d41-8c68e420804c" xlink:href="mmc-20210331.xsd#mmc_OliverWymanGroupConsultingGroupMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_15c4c5bb-bc4d-41ca-831c-41bfb4c43966" xlink:to="loc_mmc_OliverWymanGroupConsultingGroupMember_6b57950b-7a9e-4643-9d41-8c68e420804c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_6d51b363-da33-464b-a9db-9e7d18877379" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2ab1e754-5cf1-4c1f-af1f-e045bcca8df9" xlink:to="loc_us-gaap_DisaggregationOfRevenueLineItems_6d51b363-da33-464b-a9db-9e7d18877379" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_647091a7-bf3a-4874-95df-45cd88a3117a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6d51b363-da33-464b-a9db-9e7d18877379" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_647091a7-bf3a-4874-95df-45cd88a3117a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_b26c2b89-9420-431d-a911-fa70803cef0b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6d51b363-da33-464b-a9db-9e7d18877379" xlink:to="loc_us-gaap_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriod_b26c2b89-9420-431d-a911-fa70803cef0b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_1eceeec7-7596-4973-8fcb-83ba93c4bab5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_6d51b363-da33-464b-a9db-9e7d18877379" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_1eceeec7-7596-4973-8fcb-83ba93c4bab5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RevenueEstimatedRevenueExpectedtoBeRecognizedRelatedtoPerformanceObligationsDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RevenueEstimatedRevenueExpectedtoBeRecognizedRelatedtoPerformanceObligationsDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RevenueEstimatedRevenueExpectedtoBeRecognizedRelatedtoPerformanceObligationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerAbstract_fe6bedd5-f070-4b24-a09b-c018783a0442" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_fdf74ff4-4eb7-4d9b-9d1c-6d2b9b58c774" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerAbstract_fe6bedd5-f070-4b24-a09b-c018783a0442" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_fdf74ff4-4eb7-4d9b-9d1c-6d2b9b58c774" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_c6a5b973-388b-4a19-b47c-10c332755c65" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_fdf74ff4-4eb7-4d9b-9d1c-6d2b9b58c774" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_c6a5b973-388b-4a19-b47c-10c332755c65" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01020604-d5f0-4b9f-9691-9a279e6a1a89" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_fdf74ff4-4eb7-4d9b-9d1c-6d2b9b58c774" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01020604-d5f0-4b9f-9691-9a279e6a1a89" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_4f919e6c-56bb-4a25-941d-8f9be0c6977b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01020604-d5f0-4b9f-9691-9a279e6a1a89" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_4f919e6c-56bb-4a25-941d-8f9be0c6977b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_0a15ada8-d9ee-4b4e-9bf4-565436cb0bc5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_01020604-d5f0-4b9f-9691-9a279e6a1a89" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_0a15ada8-d9ee-4b4e-9bf4-565436cb0bc5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RevenueEstimatedRevenueExpectedtoBeRecognizedRelatedtoPerformanceObligationsDetails_1" xlink:type="simple" xlink:href="mmc-20210331.xsd#RevenueEstimatedRevenueExpectedtoBeRecognizedRelatedtoPerformanceObligationsDetails_1"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RevenueEstimatedRevenueExpectedtoBeRecognizedRelatedtoPerformanceObligationsDetails_1" xlink:type="extended"/>
  <link:roleRef roleURI="http://mmc.com/role/FiduciaryAssetsandLiabilities" xlink:type="simple" xlink:href="mmc-20210331.xsd#FiduciaryAssetsandLiabilities"/>
  <link:presentationLink xlink:role="http://mmc.com/role/FiduciaryAssetsandLiabilities" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiduciaryAssetsAndLiabilitiesAbstract_b2ad8e7d-3c12-4285-858c-060f2246cd90" xlink:href="mmc-20210331.xsd#mmc_FiduciaryAssetsAndLiabilitiesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiduciaryAssetsAndLiabilitiesTextBlock_64cbd452-1a22-4de9-a0ea-41bc5c3c15ec" xlink:href="mmc-20210331.xsd#mmc_FiduciaryAssetsAndLiabilitiesTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_FiduciaryAssetsAndLiabilitiesAbstract_b2ad8e7d-3c12-4285-858c-060f2246cd90" xlink:to="loc_mmc_FiduciaryAssetsAndLiabilitiesTextBlock_64cbd452-1a22-4de9-a0ea-41bc5c3c15ec" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/FiduciaryAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#FiduciaryAssetsandLiabilitiesDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/FiduciaryAssetsandLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiduciaryAssetsAndLiabilitiesAbstract_f3039319-187c-4049-b93b-04abcb96e727" xlink:href="mmc-20210331.xsd#mmc_FiduciaryAssetsAndLiabilitiesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiduciaryAssetsAndLiabilitiesTable_917cfb25-c84c-49b8-9f6e-fe76acc9a739" xlink:href="mmc-20210331.xsd#mmc_FiduciaryAssetsAndLiabilitiesTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_FiduciaryAssetsAndLiabilitiesAbstract_f3039319-187c-4049-b93b-04abcb96e727" xlink:to="loc_mmc_FiduciaryAssetsAndLiabilitiesTable_917cfb25-c84c-49b8-9f6e-fe76acc9a739" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_d89ba0ef-ee88-4818-8b7d-556d147a281a" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_FiduciaryAssetsAndLiabilitiesTable_917cfb25-c84c-49b8-9f6e-fe76acc9a739" xlink:to="loc_srt_ConsolidationItemsAxis_d89ba0ef-ee88-4818-8b7d-556d147a281a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_dfc54f8c-6371-419c-b76e-13080af5b031" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsAxis_d89ba0ef-ee88-4818-8b7d-556d147a281a" xlink:to="loc_srt_ConsolidationItemsDomain_dfc54f8c-6371-419c-b76e-13080af5b031" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_75ff6144-20c6-491d-ac50-45c975bb0416" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsDomain_dfc54f8c-6371-419c-b76e-13080af5b031" xlink:to="loc_us-gaap_OperatingSegmentsMember_75ff6144-20c6-491d-ac50-45c975bb0416" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_69445672-cd61-4b29-9f1d-d1bfbee8f600" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_FiduciaryAssetsAndLiabilitiesTable_917cfb25-c84c-49b8-9f6e-fe76acc9a739" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_69445672-cd61-4b29-9f1d-d1bfbee8f600" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_d552b900-a24c-47d1-bf0e-ea87dca4c4e0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_69445672-cd61-4b29-9f1d-d1bfbee8f600" xlink:to="loc_us-gaap_SegmentDomain_d552b900-a24c-47d1-bf0e-ea87dca4c4e0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_RiskandInsuranceServicesSegmentMember_c233bf0d-a8ec-4472-b8b7-32366fa3ac13" xlink:href="mmc-20210331.xsd#mmc_RiskandInsuranceServicesSegmentMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_d552b900-a24c-47d1-bf0e-ea87dca4c4e0" xlink:to="loc_mmc_RiskandInsuranceServicesSegmentMember_c233bf0d-a8ec-4472-b8b7-32366fa3ac13" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_ConsultingSegmentMember_1e9b4d54-c453-4b78-aaa5-6c237cb76570" xlink:href="mmc-20210331.xsd#mmc_ConsultingSegmentMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_d552b900-a24c-47d1-bf0e-ea87dca4c4e0" xlink:to="loc_mmc_ConsultingSegmentMember_1e9b4d54-c453-4b78-aaa5-6c237cb76570" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiduciaryAssetsandLiabilitiesLineItems_5e20a2ea-1d98-4439-96b5-6443abc2acd4" xlink:href="mmc-20210331.xsd#mmc_FiduciaryAssetsandLiabilitiesLineItems"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_FiduciaryAssetsAndLiabilitiesTable_917cfb25-c84c-49b8-9f6e-fe76acc9a739" xlink:to="loc_mmc_FiduciaryAssetsandLiabilitiesLineItems_5e20a2ea-1d98-4439-96b5-6443abc2acd4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_InterestIncomeFiduciaryAssets_5104fbfa-2b56-4b7a-aa3e-2bcc9ed5d070" xlink:href="mmc-20210331.xsd#mmc_InterestIncomeFiduciaryAssets"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_FiduciaryAssetsandLiabilitiesLineItems_5e20a2ea-1d98-4439-96b5-6443abc2acd4" xlink:to="loc_mmc_InterestIncomeFiduciaryAssets_5104fbfa-2b56-4b7a-aa3e-2bcc9ed5d070" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_UncollectedPremiumsandClaimsNetofRelatedPayables_bc4195e9-666b-4f05-8d87-0c20b63e5e1e" xlink:href="mmc-20210331.xsd#mmc_UncollectedPremiumsandClaimsNetofRelatedPayables"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_FiduciaryAssetsandLiabilitiesLineItems_5e20a2ea-1d98-4439-96b5-6443abc2acd4" xlink:to="loc_mmc_UncollectedPremiumsandClaimsNetofRelatedPayables_bc4195e9-666b-4f05-8d87-0c20b63e5e1e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/PerShareData" xlink:type="simple" xlink:href="mmc-20210331.xsd#PerShareData"/>
  <link:presentationLink xlink:role="http://mmc.com/role/PerShareData" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_07a07036-0137-4511-987f-1a1f01a470bf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareTextBlock_fd377432-9dc0-47db-8a71-531b56669f3e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareAbstract_07a07036-0137-4511-987f-1a1f01a470bf" xlink:to="loc_us-gaap_EarningsPerShareTextBlock_fd377432-9dc0-47db-8a71-531b56669f3e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/PerShareDataTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#PerShareDataTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/PerShareDataTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_d0845dcc-626d-4ed2-a9ec-e0b614e67d1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_21fa2b8e-0f8e-41d7-b9a1-7901efb6841f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareAbstract_d0845dcc-626d-4ed2-a9ec-e0b614e67d1e" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_21fa2b8e-0f8e-41d7-b9a1-7901efb6841f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/PerShareDataBasicandDilutedEPSCalculationContinuingOperationsDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#PerShareDataBasicandDilutedEPSCalculationContinuingOperationsDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/PerShareDataBasicandDilutedEPSCalculationContinuingOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_a9483470-6b25-439a-8802-6174561874f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_0bf30292-8811-4ddf-b1f0-6a2c68686a37" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareAbstract_a9483470-6b25-439a-8802-6174561874f9" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_0bf30292-8811-4ddf-b1f0-6a2c68686a37" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity_ba7f2da0-af6f-4b85-90d5-e40c57667474" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareAbstract_a9483470-6b25-439a-8802-6174561874f9" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity_ba7f2da0-af6f-4b85-90d5-e40c57667474" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperations_4118b426-824f-44fc-8834-24b0e53d8773" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperations"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareAbstract_a9483470-6b25-439a-8802-6174561874f9" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperations_4118b426-824f-44fc-8834-24b0e53d8773" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_abfd75fa-0489-403d-a19b-b621ebda5d61" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareAbstract_a9483470-6b25-439a-8802-6174561874f9" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_abfd75fa-0489-403d-a19b-b621ebda5d61" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_8fd5b3e7-90d5-45f8-bcda-e9dead234dbb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareAbstract_a9483470-6b25-439a-8802-6174561874f9" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_8fd5b3e7-90d5-45f8-bcda-e9dead234dbb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_4948441e-d79c-47c8-b22a-002acddc8801" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareAbstract_a9483470-6b25-439a-8802-6174561874f9" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_4948441e-d79c-47c8-b22a-002acddc8801" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_AverageSharePriceCommonStock_eb0eca6d-474e-427d-80ad-1b47fb6584c2" xlink:href="mmc-20210331.xsd#mmc_AverageSharePriceCommonStock"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EarningsPerShareAbstract_a9483470-6b25-439a-8802-6174561874f9" xlink:to="loc_mmc_AverageSharePriceCommonStock_eb0eca6d-474e-427d-80ad-1b47fb6584c2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/SupplementalDisclosurestotheConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="mmc-20210331.xsd#SupplementalDisclosurestotheConsolidatedStatementsofCashFlows"/>
  <link:presentationLink xlink:role="http://mmc.com/role/SupplementalDisclosurestotheConsolidatedStatementsofCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_39a09c8f-322d-4f65-b9fb-641628c44a6f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowSupplementalDisclosuresTextBlock_ec4fa689-7b10-47ca-bf5e-129f2f9e6993" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashFlowSupplementalDisclosuresTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_39a09c8f-322d-4f65-b9fb-641628c44a6f" xlink:to="loc_us-gaap_CashFlowSupplementalDisclosuresTextBlock_ec4fa689-7b10-47ca-bf5e-129f2f9e6993" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/SupplementalDisclosurestotheConsolidatedStatementsofCashFlowsTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#SupplementalDisclosurestotheConsolidatedStatementsofCashFlowsTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/SupplementalDisclosurestotheConsolidatedStatementsofCashFlowsTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_9ce210c6-f791-440b-b3b0-7d4a3907c270" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock_88f311be-31fe-4177-8389-22afd2514ff9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9ce210c6-f791-440b-b3b0-7d4a3907c270" xlink:to="loc_us-gaap_ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock_88f311be-31fe-4177-8389-22afd2514ff9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/SupplementalDisclosurestotheConsolidatedStatementsofCashFlowsAdditionalInformationConcerningAcquisitionsInterestAndIncomeTaxesPaidDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#SupplementalDisclosurestotheConsolidatedStatementsofCashFlowsAdditionalInformationConcerningAcquisitionsInterestAndIncomeTaxesPaidDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/SupplementalDisclosurestotheConsolidatedStatementsofCashFlowsAdditionalInformationConcerningAcquisitionsInterestAndIncomeTaxesPaidDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_8575a69f-a3fe-4bff-a586-f87595695748" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_BusinessCombinationConsiderationTransferredAssetsAcquired_c1754e45-6bd2-4353-8436-498d367f11ba" xlink:href="mmc-20210331.xsd#mmc_BusinessCombinationConsiderationTransferredAssetsAcquired"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_8575a69f-a3fe-4bff-a586-f87595695748" xlink:to="loc_mmc_BusinessCombinationConsiderationTransferredAssetsAcquired_c1754e45-6bd2-4353-8436-498d367f11ba" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_9bc08103-a41d-4d8a-bf97-2559a6b1073d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_8575a69f-a3fe-4bff-a586-f87595695748" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_9bc08103-a41d-4d8a-bf97-2559a6b1073d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_BusinessCombinationContingentandDeferredConsideration_fd61ebbc-a7a6-4af9-b2e9-2779f438dbc1" xlink:href="mmc-20210331.xsd#mmc_BusinessCombinationContingentandDeferredConsideration"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_8575a69f-a3fe-4bff-a586-f87595695748" xlink:to="loc_mmc_BusinessCombinationContingentandDeferredConsideration_fd61ebbc-a7a6-4af9-b2e9-2779f438dbc1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_26196d5c-7d4d-49a1-9338-37584979ae12" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_8575a69f-a3fe-4bff-a586-f87595695748" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_26196d5c-7d4d-49a1-9338-37584979ae12" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_1628b5b5-2cd6-4031-b55c-3c4d7831c080" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestPaidNet"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_8575a69f-a3fe-4bff-a586-f87595695748" xlink:to="loc_us-gaap_InterestPaidNet_1628b5b5-2cd6-4031-b55c-3c4d7831c080" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaidNet_af735167-5c47-4cc5-94cc-e49399fb0fec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxesPaidNet"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_8575a69f-a3fe-4bff-a586-f87595695748" xlink:to="loc_us-gaap_IncomeTaxesPaidNet_af735167-5c47-4cc5-94cc-e49399fb0fec" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/SupplementalDisclosurestotheConsolidatedStatementsofCashFlowsNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#SupplementalDisclosurestotheConsolidatedStatementsofCashFlowsNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/SupplementalDisclosurestotheConsolidatedStatementsofCashFlowsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_9804dd61-5b41-44c3-b083-d565aa93b6d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PaymentsForPreviousAcquisitionDeferredandContingentConsideration_59cb8a52-d858-4c5b-a01a-93e918891b8b" xlink:href="mmc-20210331.xsd#mmc_PaymentsForPreviousAcquisitionDeferredandContingentConsideration"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9804dd61-5b41-44c3-b083-d565aa93b6d7" xlink:to="loc_mmc_PaymentsForPreviousAcquisitionDeferredandContingentConsideration_59cb8a52-d858-4c5b-a01a-93e918891b8b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PaymentsForPreviousAcquisitionDeferredConsideration_52f88146-033e-48c1-9423-256e59d1d5d4" xlink:href="mmc-20210331.xsd#mmc_PaymentsForPreviousAcquisitionDeferredConsideration"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9804dd61-5b41-44c3-b083-d565aa93b6d7" xlink:to="loc_mmc_PaymentsForPreviousAcquisitionDeferredConsideration_52f88146-033e-48c1-9423-256e59d1d5d4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PaymentsForPreviousAcquisitionContingentConsideration_6a970d5c-7746-4a68-a4a4-4f4f252e5df3" xlink:href="mmc-20210331.xsd#mmc_PaymentsForPreviousAcquisitionContingentConsideration"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9804dd61-5b41-44c3-b083-d565aa93b6d7" xlink:to="loc_mmc_PaymentsForPreviousAcquisitionContingentConsideration_6a970d5c-7746-4a68-a4a4-4f4f252e5df3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_ProceedsFromPreviousDispositionContingentConsideration_0c932a58-57b6-445f-b01d-3645206966fa" xlink:href="mmc-20210331.xsd#mmc_ProceedsFromPreviousDispositionContingentConsideration"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9804dd61-5b41-44c3-b083-d565aa93b6d7" xlink:to="loc_mmc_ProceedsFromPreviousDispositionContingentConsideration_0c932a58-57b6-445f-b01d-3645206966fa" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PaymentofContingentConsideration_2f5bcc90-5d9b-435f-945e-c8cbc104948e" xlink:href="mmc-20210331.xsd#mmc_PaymentofContingentConsideration"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9804dd61-5b41-44c3-b083-d565aa93b6d7" xlink:to="loc_mmc_PaymentofContingentConsideration_2f5bcc90-5d9b-435f-945e-c8cbc104948e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_6b5526bd-fa8d-4938-8dc3-af51a3d20893" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9804dd61-5b41-44c3-b083-d565aa93b6d7" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_6b5526bd-fa8d-4938-8dc3-af51a3d20893" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssued1_5cb0521e-3c0c-4168-ae72-766aa6cef1a6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssued1"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9804dd61-5b41-44c3-b083-d565aa93b6d7" xlink:to="loc_us-gaap_StockIssued1_5cb0521e-3c0c-4168-ae72-766aa6cef1a6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_a8962616-6df4-4598-9538-ec2168d1f82f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_9804dd61-5b41-44c3-b083-d565aa93b6d7" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_a8962616-6df4-4598-9538-ec2168d1f82f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/OtherComprehensiveIncomeLoss" xlink:type="simple" xlink:href="mmc-20210331.xsd#OtherComprehensiveIncomeLoss"/>
  <link:presentationLink xlink:role="http://mmc.com/role/OtherComprehensiveIncomeLoss" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_d31936f6-189b-47db-afc2-b6b937710bac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNoteTextBlock_00fba6d0-28e9-4e92-975b-23baa504f831" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNoteTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_d31936f6-189b-47db-afc2-b6b937710bac" xlink:to="loc_us-gaap_ComprehensiveIncomeNoteTextBlock_00fba6d0-28e9-4e92-975b-23baa504f831" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/OtherComprehensiveIncomeLossTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#OtherComprehensiveIncomeLossTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/OtherComprehensiveIncomeLossTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_d88fc415-e1c5-45fe-bea1-396771f48f76" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock_b34e8eb4-db16-47ec-8be3-c1c17c5936d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_d88fc415-e1c5-45fe-bea1-396771f48f76" xlink:to="loc_us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock_b34e8eb4-db16-47ec-8be3-c1c17c5936d2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfComprehensiveIncomeLossTableTextBlock_9a0285e5-457e-4b3c-8864-51e0655d6fac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfComprehensiveIncomeLossTableTextBlock"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_d88fc415-e1c5-45fe-bea1-396771f48f76" xlink:to="loc_us-gaap_ScheduleOfComprehensiveIncomeLossTableTextBlock_9a0285e5-457e-4b3c-8864-51e0655d6fac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/OtherComprehensiveIncomeLossScheduleofComponentsofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#OtherComprehensiveIncomeLossScheduleofComponentsofAccumulatedOtherComprehensiveIncomeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/OtherComprehensiveIncomeLossScheduleofComponentsofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_d50b049d-ed63-4bc4-87cf-aa6fb57232e6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_0077e5cd-4740-44d2-b248-e7fd252b07f6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_d50b049d-ed63-4bc4-87cf-aa6fb57232e6" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_0077e5cd-4740-44d2-b248-e7fd252b07f6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_28da1813-757d-476d-af88-d1038b541b59" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_0077e5cd-4740-44d2-b248-e7fd252b07f6" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_28da1813-757d-476d-af88-d1038b541b59" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_254605e7-9e7f-49b1-86b6-15a2abffd2cf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_28da1813-757d-476d-af88-d1038b541b59" xlink:to="loc_us-gaap_EquityComponentDomain_254605e7-9e7f-49b1-86b6-15a2abffd2cf" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_823651fa-245b-4030-bbde-ec1479ed1993" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityComponentDomain_254605e7-9e7f-49b1-86b6-15a2abffd2cf" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_823651fa-245b-4030-bbde-ec1479ed1993" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_9a9f88e4-8474-4b6b-ab70-275f4d5128d3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_823651fa-245b-4030-bbde-ec1479ed1993" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_9a9f88e4-8474-4b6b-ab70-275f4d5128d3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_f4bcd81e-e202-4a1e-8eb8-700cf24a6fa6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_823651fa-245b-4030-bbde-ec1479ed1993" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_f4bcd81e-e202-4a1e-8eb8-700cf24a6fa6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_289fa376-c9c6-4b4d-a1b0-a2500ed702fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_0077e5cd-4740-44d2-b248-e7fd252b07f6" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_289fa376-c9c6-4b4d-a1b0-a2500ed702fd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e9e59e-7467-4aec-a164-be510dd24ca5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_289fa376-c9c6-4b4d-a1b0-a2500ed702fd" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e9e59e-7467-4aec-a164-be510dd24ca5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_5942afac-fa72-4edc-8681-006fd8953df1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e9e59e-7467-4aec-a164-be510dd24ca5" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_5942afac-fa72-4edc-8681-006fd8953df1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_f81f491e-57b1-4e82-8899-0338a41281ae" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e9e59e-7467-4aec-a164-be510dd24ca5" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_f81f491e-57b1-4e82-8899-0338a41281ae" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_c25c45a0-ea77-419c-ba92-957ddf7c3046" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e9e59e-7467-4aec-a164-be510dd24ca5" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_c25c45a0-ea77-419c-ba92-957ddf7c3046" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_ceab2ff6-9d2f-49e7-a2da-16a900ff0112" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e9e59e-7467-4aec-a164-be510dd24ca5" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_ceab2ff6-9d2f-49e7-a2da-16a900ff0112" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_963b06ef-48c5-4ab7-acac-5b1dbbbfb3bf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_a0e9e59e-7467-4aec-a164-be510dd24ca5" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_963b06ef-48c5-4ab7-acac-5b1dbbbfb3bf" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/OtherComprehensiveIncomeLossScheduleOfComponentsOfComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#OtherComprehensiveIncomeLossScheduleOfComponentsOfComprehensiveIncomeLossDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/OtherComprehensiveIncomeLossScheduleOfComponentsOfComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_002264ef-5b7b-4011-9fa5-08a9e7a0a650" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax_c20469e9-ff6c-4579-ac3e-a74c3b475ce1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_002264ef-5b7b-4011-9fa5-08a9e7a0a650" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentBeforeTax_c20469e9-ff6c-4579-ac3e-a74c3b475ce1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_7e2d4076-5ec5-4f23-9159-19d6a4f956b1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_002264ef-5b7b-4011-9fa5-08a9e7a0a650" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_7e2d4076-5ec5-4f23-9159-19d6a4f956b1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_8c6fbb88-ca2f-4ef3-be6e-27089fc1936e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_002264ef-5b7b-4011-9fa5-08a9e7a0a650" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_8c6fbb88-ca2f-4ef3-be6e-27089fc1936e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_002264ef-5b7b-4011-9fa5-08a9e7a0a650" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax_31fa6760-536e-432a-beeb-878cc4ce71bf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax_31fa6760-536e-432a-beeb-878cc4ce71bf" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax_e785bac2-1af8-4f09-944c-f9548b68a75d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax_e785bac2-1af8-4f09-944c-f9548b68a75d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_2dd2b92c-8894-45a2-a020-143c440e8186" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_2dd2b92c-8894-45a2-a020-143c440e8186" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTotalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax_5394e269-382e-474f-a053-a53bf6fd4265" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax_5394e269-382e-474f-a053-a53bf6fd4265" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax_02d1f8f6-eaa7-4d56-b28c-097c3835a9ae" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax_02d1f8f6-eaa7-4d56-b28c-097c3835a9ae" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax_3ad3192c-3788-4cfe-9f56-c37aef970e56" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax_3ad3192c-3788-4cfe-9f56-c37aef970e56" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentBeforeTax_f1794715-4c3e-463f-a980-4fe9b78385f4" xlink:href="mmc-20210331.xsd#mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentBeforeTax"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentBeforeTax_f1794715-4c3e-463f-a980-4fe9b78385f4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentTax_f8ae350c-59db-4743-b3fa-836a71d7cfa0" xlink:href="mmc-20210331.xsd#mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentTax"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentTax_f8ae350c-59db-4743-b3fa-836a71d7cfa0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentNetofTax_87194780-284b-4e05-a1ce-2fd299890b0f" xlink:href="mmc-20210331.xsd#mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentNetofTax"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansForeignCurrencyTransactionandTranslationAdjustmentNetofTax_87194780-284b-4e05-a1ce-2fd299890b0f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherComprehensiveIncomeLossAdjustmentFromMergerofPensionPlansPensionandPostretirementBenefitPlansBeforeTax_cf0108b9-abab-41df-b272-732600b7eb55" xlink:href="mmc-20210331.xsd#mmc_OtherComprehensiveIncomeLossAdjustmentFromMergerofPensionPlansPensionandPostretirementBenefitPlansBeforeTax"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_mmc_OtherComprehensiveIncomeLossAdjustmentFromMergerofPensionPlansPensionandPostretirementBenefitPlansBeforeTax_cf0108b9-abab-41df-b272-732600b7eb55" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherComprehensiveIncomeLossAdjustmentFromMergerofPensionPlansPensionandOtherPostretirementBenefitPlansTax_ee8f82d1-f8ad-4a17-bf65-e64c7d188c6e" xlink:href="mmc-20210331.xsd#mmc_OtherComprehensiveIncomeLossAdjustmentFromMergerofPensionPlansPensionandOtherPostretirementBenefitPlansTax"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_mmc_OtherComprehensiveIncomeLossAdjustmentFromMergerofPensionPlansPensionandOtherPostretirementBenefitPlansTax_ee8f82d1-f8ad-4a17-bf65-e64c7d188c6e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherComprehensiveIncomeLossAdjustmentFromMergerofPensionPlansPensionandOtherPostretirementBenefitPlansNetofTax_ae19d9a1-5538-4704-b037-f15644009731" xlink:href="mmc-20210331.xsd#mmc_OtherComprehensiveIncomeLossAdjustmentFromMergerofPensionPlansPensionandOtherPostretirementBenefitPlansNetofTax"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_mmc_OtherComprehensiveIncomeLossAdjustmentFromMergerofPensionPlansPensionandOtherPostretirementBenefitPlansNetofTax_ae19d9a1-5538-4704-b037-f15644009731" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansRemeasurementAdjustmentBeforeTax_9f4cb9c5-21ab-4c0b-8100-45ae3a225df2" xlink:href="mmc-20210331.xsd#mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansRemeasurementAdjustmentBeforeTax"/>
    <link:presentationArc order="13" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansRemeasurementAdjustmentBeforeTax_9f4cb9c5-21ab-4c0b-8100-45ae3a225df2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansRemeasurementAdjustmentTax_3599d91a-8bd8-4e65-9241-c6c30be66835" xlink:href="mmc-20210331.xsd#mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansRemeasurementAdjustmentTax"/>
    <link:presentationArc order="14" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansRemeasurementAdjustmentTax_3599d91a-8bd8-4e65-9241-c6c30be66835" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansRemeasurementAdjustmentNetofTax_bb5e990f-bc11-4618-97d4-1c59e440d68c" xlink:href="mmc-20210331.xsd#mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansRemeasurementAdjustmentNetofTax"/>
    <link:presentationArc order="15" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_mmc_OtherComprehensiveIncomeLossPensionandOtherPostretirementBenefitPlansRemeasurementAdjustmentNetofTax_bb5e990f-bc11-4618-97d4-1c59e440d68c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_319d178f-2540-4bb0-a8d0-d3126a3d08ff" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax"/>
    <link:presentationArc order="16" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax_319d178f-2540-4bb0-a8d0-d3126a3d08ff" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTotalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_f01a1739-63d4-4275-9a51-1b59093354c6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax"/>
    <link:presentationArc order="17" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_f01a1739-63d4-4275-9a51-1b59093354c6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTotalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_c669ef6b-dd52-4b16-ab50-a18bb353b255" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
    <link:presentationArc order="18" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_d0bb444f-7f97-4850-adc8-707ea1732cfd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_c669ef6b-dd52-4b16-ab50-a18bb353b255" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTotalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_c97f237c-86f6-4c27-94a7-f8872c3f6d2e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTax"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_002264ef-5b7b-4011-9fa5-08a9e7a0a650" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_c97f237c-86f6-4c27-94a7-f8872c3f6d2e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_8e1ac231-c3e3-4d49-9cc7-613efd61a7a2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossTax"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_002264ef-5b7b-4011-9fa5-08a9e7a0a650" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_8e1ac231-c3e3-4d49-9cc7-613efd61a7a2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_7a14aaa9-5d7e-479b-a356-79e6cb5a02d4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_002264ef-5b7b-4011-9fa5-08a9e7a0a650" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_7a14aaa9-5d7e-479b-a356-79e6cb5a02d4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/OtherComprehensiveIncomeLossScheduleOfComponentsOfComprehensiveIncomeLossDetails_1" xlink:type="simple" xlink:href="mmc-20210331.xsd#OtherComprehensiveIncomeLossScheduleOfComponentsOfComprehensiveIncomeLossDetails_1"/>
  <link:presentationLink xlink:role="http://mmc.com/role/OtherComprehensiveIncomeLossScheduleOfComponentsOfComprehensiveIncomeLossDetails_1" xlink:type="extended"/>
  <link:roleRef roleURI="http://mmc.com/role/AcquisitionsandDispositions" xlink:type="simple" xlink:href="mmc-20210331.xsd#AcquisitionsandDispositions"/>
  <link:presentationLink xlink:role="http://mmc.com/role/AcquisitionsandDispositions" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationsAbstract_c40b6f73-d4fb-4cac-8e8e-f640d25067ba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MergersAcquisitionsAndDispositionsDisclosuresTextBlock_b783f7d5-61a8-4e27-9649-7e9d27cf3078" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MergersAcquisitionsAndDispositionsDisclosuresTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessCombinationsAbstract_c40b6f73-d4fb-4cac-8e8e-f640d25067ba" xlink:to="loc_us-gaap_MergersAcquisitionsAndDispositionsDisclosuresTextBlock_b783f7d5-61a8-4e27-9649-7e9d27cf3078" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/AcquisitionsandDispositionsTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#AcquisitionsandDispositionsTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/AcquisitionsandDispositionsTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationsAbstract_b74ff95e-8635-44b9-8132-509d8f141b49" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaInformationTextBlock_c1b9a69a-753e-46fd-a478-02003ae17a59" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionProFormaInformationTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessCombinationsAbstract_b74ff95e-8635-44b9-8132-509d8f141b49" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaInformationTextBlock_c1b9a69a-753e-46fd-a478-02003ae17a59" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/AcquisitionsandDispositionsNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#AcquisitionsandDispositionsNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/AcquisitionsandDispositionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationsAbstract_13561d06-e3bf-4c1e-9bc6-3f892f77409a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a050e04e-6dfc-488e-b222-734da7297a4a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessCombinationsAbstract_13561d06-e3bf-4c1e-9bc6-3f892f77409a" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a050e04e-6dfc-488e-b222-734da7297a4a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b650d29b-ffae-4c63-8da3-71588cb0dc39" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a050e04e-6dfc-488e-b222-734da7297a4a" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b650d29b-ffae-4c63-8da3-71588cb0dc39" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a153e593-6863-4b97-85b7-f9474e8d43bb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_b650d29b-ffae-4c63-8da3-71588cb0dc39" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a153e593-6863-4b97-85b7-f9474e8d43bb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_CertainBusinessesPrimarilyintheU.S.U.K.andCanadaMember_600c185e-a2cf-4680-9dd5-340ee1a912e3" xlink:href="mmc-20210331.xsd#mmc_CertainBusinessesPrimarilyintheU.S.U.K.andCanadaMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a153e593-6863-4b97-85b7-f9474e8d43bb" xlink:to="loc_mmc_CertainBusinessesPrimarilyintheU.S.U.K.andCanadaMember_600c185e-a2cf-4680-9dd5-340ee1a912e3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_a0c8ef33-7a5d-45b1-ad0f-74d7de0fa085" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a050e04e-6dfc-488e-b222-734da7297a4a" xlink:to="loc_srt_RangeAxis_a0c8ef33-7a5d-45b1-ad0f-74d7de0fa085" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f2f803f1-6e80-465a-bfda-bfd589dab5de" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeAxis_a0c8ef33-7a5d-45b1-ad0f-74d7de0fa085" xlink:to="loc_srt_RangeMember_f2f803f1-6e80-465a-bfda-bfd589dab5de" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_0855d3b3-c677-4019-ae48-55e513ee06b9" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeMember_f2f803f1-6e80-465a-bfda-bfd589dab5de" xlink:to="loc_srt_MinimumMember_0855d3b3-c677-4019-ae48-55e513ee06b9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_caf46bc6-d23d-4562-91a1-ea1df2779fb1" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeMember_f2f803f1-6e80-465a-bfda-bfd589dab5de" xlink:to="loc_srt_MaximumMember_caf46bc6-d23d-4562-91a1-ea1df2779fb1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_4cbb4465-53d3-48b0-9d9b-88b9705ce087" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a050e04e-6dfc-488e-b222-734da7297a4a" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_4cbb4465-53d3-48b0-9d9b-88b9705ce087" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_bc52d910-83a6-4605-b8cf-e67cbdf022ab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_4cbb4465-53d3-48b0-9d9b-88b9705ce087" xlink:to="loc_us-gaap_SegmentDomain_bc52d910-83a6-4605-b8cf-e67cbdf022ab" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_RiskandInsuranceServicesSegmentMember_44bcae66-6062-44ef-87e8-d1668df4d228" xlink:href="mmc-20210331.xsd#mmc_RiskandInsuranceServicesSegmentMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_bc52d910-83a6-4605-b8cf-e67cbdf022ab" xlink:to="loc_mmc_RiskandInsuranceServicesSegmentMember_44bcae66-6062-44ef-87e8-d1668df4d228" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_aad6e875-f2c8-4ff4-b940-dd4ad9fa87fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a050e04e-6dfc-488e-b222-734da7297a4a" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_aad6e875-f2c8-4ff4-b940-dd4ad9fa87fc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2f54c33b-3691-4d56-8e6c-bf295f45a3b3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_aad6e875-f2c8-4ff4-b940-dd4ad9fa87fc" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2f54c33b-3691-4d56-8e6c-bf295f45a3b3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PriorFiscalPeriodsAcquisitionsMember_af06e264-99fd-421a-a839-08d4a648ef6a" xlink:href="mmc-20210331.xsd#mmc_PriorFiscalPeriodsAcquisitionsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2f54c33b-3691-4d56-8e6c-bf295f45a3b3" xlink:to="loc_mmc_PriorFiscalPeriodsAcquisitionsMember_af06e264-99fd-421a-a839-08d4a648ef6a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a050e04e-6dfc-488e-b222-734da7297a4a" xlink:to="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfBusinessesAcquired_8ac0560c-eef0-4d6e-93ae-3fdfc3f88f77" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NumberOfBusinessesAcquired"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_us-gaap_NumberOfBusinessesAcquired_8ac0560c-eef0-4d6e-93ae-3fdfc3f88f77" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PaymentsForPreviousAcquisitionDeferredConsideration_fc890261-ba25-42f5-ad61-9851fd83246b" xlink:href="mmc-20210331.xsd#mmc_PaymentsForPreviousAcquisitionDeferredConsideration"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_mmc_PaymentsForPreviousAcquisitionDeferredConsideration_fc890261-ba25-42f5-ad61-9851fd83246b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PaymentsForPreviousAcquisitionContingentConsideration_26dbee75-85e8-450a-a374-c88bdc849de7" xlink:href="mmc-20210331.xsd#mmc_PaymentsForPreviousAcquisitionContingentConsideration"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_mmc_PaymentsForPreviousAcquisitionContingentConsideration_26dbee75-85e8-450a-a374-c88bdc849de7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_3736d444-c851-47cd-905b-c69ba151b9a2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_3736d444-c851-47cd-905b-c69ba151b9a2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_5ac3a0c0-6ce1-40bf-8b80-ec385d2f8541" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_5ac3a0c0-6ce1-40bf-8b80-ec385d2f8541" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_728166ad-caa7-4a41-8745-17f10d418abc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_728166ad-caa7-4a41-8745-17f10d418abc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_BusinessCombinationContingentandDeferredConsideration_8b17dd28-d991-43c2-81c2-b7a566244c0f" xlink:href="mmc-20210331.xsd#mmc_BusinessCombinationContingentandDeferredConsideration"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_mmc_BusinessCombinationContingentandDeferredConsideration_8b17dd28-d991-43c2-81c2-b7a566244c0f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_BusinessCombinationContingentConsiderationArrangementsRevenueTargetPeriod_2fea2728-e2a6-4dd0-a90b-3de974ec3077" xlink:href="mmc-20210331.xsd#mmc_BusinessCombinationContingentConsiderationArrangementsRevenueTargetPeriod"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_mmc_BusinessCombinationContingentConsiderationArrangementsRevenueTargetPeriod_2fea2728-e2a6-4dd0-a90b-3de974ec3077" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_b1b33c68-4e4a-4689-a1ce-bd19cff47cd8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_b1b33c68-4e4a-4689-a1ce-bd19cff47cd8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_856bb366-80c7-4078-8922-9fdb7c13426d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_1efbb1f5-86fa-460d-9665-ce19b3ff1759" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual_856bb366-80c7-4078-8922-9fdb7c13426d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/AcquisitionsandDispositionsProFormaInformationDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#AcquisitionsandDispositionsProFormaInformationDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/AcquisitionsandDispositionsProFormaInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationsAbstract_f049ac72-9d9e-4407-a0db-56340c6c5dd4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_cf496dc0-d7a6-4894-964e-8fb521f09eb9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaRevenue"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessCombinationsAbstract_f049ac72-9d9e-4407-a0db-56340c6c5dd4" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaRevenue_cf496dc0-d7a6-4894-964e-8fb521f09eb9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_c16b7911-c44e-4d8b-9358-466129a83382" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessCombinationsAbstract_f049ac72-9d9e-4407-a0db-56340c6c5dd4" xlink:to="loc_us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss_c16b7911-c44e-4d8b-9358-466129a83382" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareBasic_10c00180-af11-487c-be89-cd7af255e6c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareBasic"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessCombinationsAbstract_f049ac72-9d9e-4407-a0db-56340c6c5dd4" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareBasic_10c00180-af11-487c-be89-cd7af255e6c5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareDiluted_83933084-6ef1-4810-a50c-cf1dd491cb06" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareDiluted"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessCombinationsAbstract_f049ac72-9d9e-4407-a0db-56340c6c5dd4" xlink:to="loc_us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareDiluted_83933084-6ef1-4810-a50c-cf1dd491cb06" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/GoodwillandOtherIntangibles" xlink:type="simple" xlink:href="mmc-20210331.xsd#GoodwillandOtherIntangibles"/>
  <link:presentationLink xlink:role="http://mmc.com/role/GoodwillandOtherIntangibles" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_cbe996f9-f508-4761-9e29-abb91c4a9a55" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock_e590f4be-1425-4b66-8f93-a22aec805ad3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_cbe996f9-f508-4761-9e29-abb91c4a9a55" xlink:to="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock_e590f4be-1425-4b66-8f93-a22aec805ad3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/GoodwillandOtherIntangiblesTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#GoodwillandOtherIntangiblesTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/GoodwillandOtherIntangiblesTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_1f5642b5-77a9-4e79-97d4-380d8f533e7d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTextBlock_124cb93e-707f-48c1-94dd-94e7210f01ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfGoodwillTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_1f5642b5-77a9-4e79-97d4-380d8f533e7d" xlink:to="loc_us-gaap_ScheduleOfGoodwillTextBlock_124cb93e-707f-48c1-94dd-94e7210f01ac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock_2dfd94a0-8011-4a54-8625-fb52939b4254" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_1f5642b5-77a9-4e79-97d4-380d8f533e7d" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock_2dfd94a0-8011-4a54-8625-fb52939b4254" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleofFiniteLivedIntangibleAssetsFutureAmortizationExpenseTableTextBlock_474b27bc-ee3e-4a99-8f5a-950fa634f64d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleofFiniteLivedIntangibleAssetsFutureAmortizationExpenseTableTextBlock"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_1f5642b5-77a9-4e79-97d4-380d8f533e7d" xlink:to="loc_us-gaap_ScheduleofFiniteLivedIntangibleAssetsFutureAmortizationExpenseTableTextBlock_474b27bc-ee3e-4a99-8f5a-950fa634f64d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/GoodwillandOtherIntangiblesChangesintheCarryingAmountofGoodwillDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#GoodwillandOtherIntangiblesChangesintheCarryingAmountofGoodwillDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/GoodwillandOtherIntangiblesChangesintheCarryingAmountofGoodwillDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_635ee7cf-7c16-490c-8f20-453b4b7dbeb7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_a8171d0b-720c-4b53-8db6-5a960828ce3b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillRollForward"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_635ee7cf-7c16-490c-8f20-453b4b7dbeb7" xlink:to="loc_us-gaap_GoodwillRollForward_a8171d0b-720c-4b53-8db6-5a960828ce3b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_b34cbce4-9544-484e-ad36-b8900394fc88" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillRollForward_a8171d0b-720c-4b53-8db6-5a960828ce3b" xlink:to="loc_us-gaap_Goodwill_b34cbce4-9544-484e-ad36-b8900394fc88" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_66e443bd-78ed-4089-a52a-56d44c15414e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillRollForward_a8171d0b-720c-4b53-8db6-5a960828ce3b" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_66e443bd-78ed-4089-a52a-56d44c15414e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillOtherIncreaseDecrease_836cea89-6f26-4269-ae8d-3e584b0e2500" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillOtherIncreaseDecrease"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillRollForward_a8171d0b-720c-4b53-8db6-5a960828ce3b" xlink:to="loc_us-gaap_GoodwillOtherIncreaseDecrease_836cea89-6f26-4269-ae8d-3e584b0e2500" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_aafe763a-e33d-4f68-a63a-9cb91c0d2192" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillRollForward_a8171d0b-720c-4b53-8db6-5a960828ce3b" xlink:to="loc_us-gaap_Goodwill_aafe763a-e33d-4f68-a63a-9cb91c0d2192" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/GoodwillandOtherIntangiblesNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#GoodwillandOtherIntangiblesNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/GoodwillandOtherIntangiblesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_7893f5ff-5ae3-4369-ba17-dc5aa03705ae" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_80a360e7-b516-4db0-844b-30d1bb019a0e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_7893f5ff-5ae3-4369-ba17-dc5aa03705ae" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_80a360e7-b516-4db0-844b-30d1bb019a0e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_511c0461-6014-4606-bf64-2724093f90b3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_80a360e7-b516-4db0-844b-30d1bb019a0e" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_511c0461-6014-4606-bf64-2724093f90b3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_644b99bd-9569-4d7a-bc57-b5966f028533" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_511c0461-6014-4606-bf64-2724093f90b3" xlink:to="loc_us-gaap_SegmentDomain_644b99bd-9569-4d7a-bc57-b5966f028533" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_RiskandInsuranceServicesSegmentMember_357eff63-a777-4915-8ed5-d09b284df16d" xlink:href="mmc-20210331.xsd#mmc_RiskandInsuranceServicesSegmentMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_644b99bd-9569-4d7a-bc57-b5966f028533" xlink:to="loc_mmc_RiskandInsuranceServicesSegmentMember_357eff63-a777-4915-8ed5-d09b284df16d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_ConsultingSegmentMember_cd29ac0f-fe89-432e-958e-e713b0271321" xlink:href="mmc-20210331.xsd#mmc_ConsultingSegmentMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_644b99bd-9569-4d7a-bc57-b5966f028533" xlink:to="loc_mmc_ConsultingSegmentMember_cd29ac0f-fe89-432e-958e-e713b0271321" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_0de2261c-eb3a-47a2-a001-349eab460320" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_80a360e7-b516-4db0-844b-30d1bb019a0e" xlink:to="loc_us-gaap_SegmentReportingInformationLineItems_0de2261c-eb3a-47a2-a001-349eab460320" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_d3cf2326-2475-4d4a-b68f-bddbfe7066c2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0de2261c-eb3a-47a2-a001-349eab460320" xlink:to="loc_us-gaap_Goodwill_d3cf2326-2475-4d4a-b68f-bddbfe7066c2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_42cd68e1-2420-4cef-8de6-157c54c67f27" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0de2261c-eb3a-47a2-a001-349eab460320" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_42cd68e1-2420-4cef-8de6-157c54c67f27" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/GoodwillandOtherIntangiblesAmortizedIntangibleAssetsDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#GoodwillandOtherIntangiblesAmortizedIntangibleAssetsDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/GoodwillandOtherIntangiblesAmortizedIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_cb9be8c5-4429-48a3-a2bc-bbc91fe42b43" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_ddf8baf8-014b-4b76-8670-ae386642850e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_cb9be8c5-4429-48a3-a2bc-bbc91fe42b43" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_ddf8baf8-014b-4b76-8670-ae386642850e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e6a812a6-5d4a-4e48-a0f3-e641c0e916f4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_ddf8baf8-014b-4b76-8670-ae386642850e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e6a812a6-5d4a-4e48-a0f3-e641c0e916f4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5bc1633e-5cb2-4f81-8382-e84d7a94f540" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e6a812a6-5d4a-4e48-a0f3-e641c0e916f4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5bc1633e-5cb2-4f81-8382-e84d7a94f540" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_c81dc347-6cb4-4ea5-a135-d608bf029fb1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5bc1633e-5cb2-4f81-8382-e84d7a94f540" xlink:to="loc_us-gaap_CustomerRelationshipsMember_c81dc347-6cb4-4ea5-a135-d608bf029fb1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_617c3cc1-ddb2-4fb5-bd0f-11eccaf9ec5e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5bc1633e-5cb2-4f81-8382-e84d7a94f540" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_617c3cc1-ddb2-4fb5-bd0f-11eccaf9ec5e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_aae24771-134d-4d38-b811-e42206c8cf63" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_ddf8baf8-014b-4b76-8670-ae386642850e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_aae24771-134d-4d38-b811-e42206c8cf63" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_a41026d2-b736-4ff2-b7f9-03d13196514c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_aae24771-134d-4d38-b811-e42206c8cf63" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_a41026d2-b736-4ff2-b7f9-03d13196514c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_82ec317d-2acd-4512-84c0-33c102664496" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_aae24771-134d-4d38-b811-e42206c8cf63" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_82ec317d-2acd-4512-84c0-33c102664496" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_4e6ac4e9-ae37-41dc-909d-943d79f0ce9f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_aae24771-134d-4d38-b811-e42206c8cf63" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_4e6ac4e9-ae37-41dc-909d-943d79f0ce9f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/GoodwillAndOtherIntangiblesEstimatedFutureAggregateAmortizationExpenseDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#GoodwillAndOtherIntangiblesEstimatedFutureAggregateAmortizationExpenseDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/GoodwillAndOtherIntangiblesEstimatedFutureAggregateAmortizationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_48447685-583d-42c4-9523-92310c39c783" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_c5626316-5689-4b07-be33-3f74857620f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_48447685-583d-42c4-9523-92310c39c783" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_c5626316-5689-4b07-be33-3f74857620f9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_0044e2ca-9214-4f99-8ce5-3235f255588d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_48447685-583d-42c4-9523-92310c39c783" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_0044e2ca-9214-4f99-8ce5-3235f255588d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_6cfeb231-1c6b-4f75-8e13-360aa8b1d505" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_48447685-583d-42c4-9523-92310c39c783" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_6cfeb231-1c6b-4f75-8e13-360aa8b1d505" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_4f84eccf-9fec-401f-b738-2ea17e6f5438" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_48447685-583d-42c4-9523-92310c39c783" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_4f84eccf-9fec-401f-b738-2ea17e6f5438" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_82a7d233-e408-4504-8d01-e7742e96de74" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_48447685-583d-42c4-9523-92310c39c783" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_82a7d233-e408-4504-8d01-e7742e96de74" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiniteLivedIntangibleAssetExpectedAmortizationafterYearFour_03607dcf-0dde-4605-87a0-e40ced15d818" xlink:href="mmc-20210331.xsd#mmc_FiniteLivedIntangibleAssetExpectedAmortizationafterYearFour"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_48447685-583d-42c4-9523-92310c39c783" xlink:to="loc_mmc_FiniteLivedIntangibleAssetExpectedAmortizationafterYearFour_03607dcf-0dde-4605-87a0-e40ced15d818" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_71b391cd-21c6-4d8f-bcde-94adeebf7bce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_48447685-583d-42c4-9523-92310c39c783" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_71b391cd-21c6-4d8f-bcde-94adeebf7bce" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/FairValueMeasurements" xlink:type="simple" xlink:href="mmc-20210331.xsd#FairValueMeasurements"/>
  <link:presentationLink xlink:role="http://mmc.com/role/FairValueMeasurements" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosuresAbstract_996be186-baaf-4d24-a48b-f6ca12b90f9e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosuresTextBlock_50a23657-2082-489d-adb7-4bd8ee05ad4f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueDisclosuresAbstract_996be186-baaf-4d24-a48b-f6ca12b90f9e" xlink:to="loc_us-gaap_FairValueDisclosuresTextBlock_50a23657-2082-489d-adb7-4bd8ee05ad4f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/FairValueMeasurementsTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#FairValueMeasurementsTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/FairValueMeasurementsTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosuresAbstract_858e9c20-270a-44f5-8567-b2fe825d3d56" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_e61ebf66-2c04-45bd-9d5c-f65fbd3ea76c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueDisclosuresAbstract_858e9c20-270a-44f5-8567-b2fe825d3d56" xlink:to="loc_us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_e61ebf66-2c04-45bd-9d5c-f65fbd3ea76c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_edb2e1ed-f6fa-4b06-a469-01db3c92e4e6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueDisclosuresAbstract_858e9c20-270a-44f5-8567-b2fe825d3d56" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_edb2e1ed-f6fa-4b06-a469-01db3c92e4e6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/FairValueMeasurementsNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#FairValueMeasurementsNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/FairValueMeasurementsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosuresAbstract_ddce054e-b390-45aa-bf83-5e02b180b116" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_708fda79-f64b-4669-9e92-4c1e5a86044d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueDisclosuresAbstract_ddce054e-b390-45aa-bf83-5e02b180b116" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_708fda79-f64b-4669-9e92-4c1e5a86044d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_4ac5e1b2-b9db-4ed1-a5c3-f8b83108baf9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_708fda79-f64b-4669-9e92-4c1e5a86044d" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_4ac5e1b2-b9db-4ed1-a5c3-f8b83108baf9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_d8f11f7b-e1b3-4590-83dd-42309997b76d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_4ac5e1b2-b9db-4ed1-a5c3-f8b83108baf9" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_d8f11f7b-e1b3-4590-83dd-42309997b76d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_d4652da6-75f1-4867-bf32-b8b99bcb3efa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_d8f11f7b-e1b3-4590-83dd-42309997b76d" xlink:to="loc_us-gaap_MoneyMarketFundsMember_d4652da6-75f1-4867-bf32-b8b99bcb3efa" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_ab81eb16-e06f-444d-b56a-552821d9f168" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_708fda79-f64b-4669-9e92-4c1e5a86044d" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_ab81eb16-e06f-444d-b56a-552821d9f168" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_02b613f1-4002-4776-bcf8-99ba4fdf8dab" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_ab81eb16-e06f-444d-b56a-552821d9f168" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_02b613f1-4002-4776-bcf8-99ba4fdf8dab" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_AlexanderForbesGroupHoldingsLimitedMember_30bc4409-1b23-4457-9832-863ac3ecd5e0" xlink:href="mmc-20210331.xsd#mmc_AlexanderForbesGroupHoldingsLimitedMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_02b613f1-4002-4776-bcf8-99ba4fdf8dab" xlink:to="loc_mmc_AlexanderForbesGroupHoldingsLimitedMember_30bc4409-1b23-4457-9832-863ac3ecd5e0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_48c6bc0a-b38e-41a1-9e99-7d3b53103f78" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_708fda79-f64b-4669-9e92-4c1e5a86044d" xlink:to="loc_us-gaap_InvestmentTypeAxis_48c6bc0a-b38e-41a1-9e99-7d3b53103f78" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_bfa93ced-53a8-4001-a429-1909b1d7d4c6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_InvestmentTypeAxis_48c6bc0a-b38e-41a1-9e99-7d3b53103f78" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_bfa93ced-53a8-4001-a429-1909b1d7d4c6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_PrivateInsuranceandConsultingMember_aaf90e1c-2378-4629-84c3-36215bf60fe9" xlink:href="mmc-20210331.xsd#mmc_PrivateInsuranceandConsultingMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_bfa93ced-53a8-4001-a429-1909b1d7d4c6" xlink:to="loc_mmc_PrivateInsuranceandConsultingMember_aaf90e1c-2378-4629-84c3-36215bf60fe9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrivateEquityFundsMember_22d3e871-0d85-49bd-a30b-02120ac43282" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrivateEquityFundsMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_bfa93ced-53a8-4001-a429-1909b1d7d4c6" xlink:to="loc_us-gaap_PrivateEquityFundsMember_22d3e871-0d85-49bd-a30b-02120ac43282" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_36810db1-62b4-4096-9d6b-1189d0d9aecd" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_708fda79-f64b-4669-9e92-4c1e5a86044d" xlink:to="loc_srt_RangeAxis_36810db1-62b4-4096-9d6b-1189d0d9aecd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_e2617420-2aab-4319-ac3b-9734faf38d1e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeAxis_36810db1-62b4-4096-9d6b-1189d0d9aecd" xlink:to="loc_srt_RangeMember_e2617420-2aab-4319-ac3b-9734faf38d1e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_3ad2b95c-63e5-4859-91de-1ef5d58bdf8c" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeMember_e2617420-2aab-4319-ac3b-9734faf38d1e" xlink:to="loc_srt_MinimumMember_3ad2b95c-63e5-4859-91de-1ef5d58bdf8c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_29f40d92-5ee8-40d7-8350-10af5559c051" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeMember_e2617420-2aab-4319-ac3b-9734faf38d1e" xlink:to="loc_srt_MaximumMember_29f40d92-5ee8-40d7-8350-10af5559c051" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_708fda79-f64b-4669-9e92-4c1e5a86044d" xlink:to="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_d3c698bd-6d7c-47f1-989c-6e078fa68673" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharePrice"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:to="loc_us-gaap_SharePrice_d3c698bd-6d7c-47f1-989c-6e078fa68673" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_BusinessCombinationContingentConsiderationArrangementsRevenueTargetPeriod_915cd64a-0eab-4c3d-94c3-ddbb28c17099" xlink:href="mmc-20210331.xsd#mmc_BusinessCombinationContingentConsiderationArrangementsRevenueTargetPeriod"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:to="loc_mmc_BusinessCombinationContingentConsiderationArrangementsRevenueTargetPeriod_915cd64a-0eab-4c3d-94c3-ddbb28c17099" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_392a282a-08d7-43f4-a7c8-f2bd0f300fb5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestments"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:to="loc_us-gaap_EquityMethodInvestments_392a282a-08d7-43f4-a7c8-f2bd0f300fb5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_4af77dd6-eaea-4782-9d64-ed02c4e4cb97" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_4af77dd6-eaea-4782-9d64-ed02c4e4cb97" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_4b13d1db-bc66-4047-a2c6-b3e47c8a9ad5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_4b13d1db-bc66-4047-a2c6-b3e47c8a9ad5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_1611c90d-876e-475e-b720-864b40023686" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_1611c90d-876e-475e-b720-864b40023686" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_146d1906-ecde-4b8c-a13f-cc6b51cc37e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_146d1906-ecde-4b8c-a13f-cc6b51cc37e7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_f36ec667-eba8-4c9b-882c-debd480233f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_42abf012-99f1-46d1-a952-1cd778f9c0da" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_f36ec667-eba8-4c9b-882c-debd480233f5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/FairValueMeasurementsAssetsAndLiabilitiesMeasuredAtFairValueOnARecurringBasisDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#FairValueMeasurementsAssetsAndLiabilitiesMeasuredAtFairValueOnARecurringBasisDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/FairValueMeasurementsAssetsAndLiabilitiesMeasuredAtFairValueOnARecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosuresAbstract_cfeaeea8-e31c-456a-996c-b3524eb4a2be" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_204e459c-5449-4222-9262-4ef1641e7cd8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueDisclosuresAbstract_cfeaeea8-e31c-456a-996c-b3524eb4a2be" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_204e459c-5449-4222-9262-4ef1641e7cd8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_c9fd38af-e4a8-4066-bc60-a8fb614c23ea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_204e459c-5449-4222-9262-4ef1641e7cd8" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_c9fd38af-e4a8-4066-bc60-a8fb614c23ea" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_e05b10fa-b2c5-4371-aacf-1393b658e1f7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_c9fd38af-e4a8-4066-bc60-a8fb614c23ea" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_e05b10fa-b2c5-4371-aacf-1393b658e1f7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMember_3936d490-2056-4a1c-a4f1-093b9ca30a1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e05b10fa-b2c5-4371-aacf-1393b658e1f7" xlink:to="loc_us-gaap_OtherAssetsMember_3936d490-2056-4a1c-a4f1-093b9ca30a1e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_01b40b05-a46f-4c24-a566-908be2c563ef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e05b10fa-b2c5-4371-aacf-1393b658e1f7" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_01b40b05-a46f-4c24-a566-908be2c563ef" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherReceivablesMember_0f884b1e-6fa0-4961-a6c8-54e1373efcb0" xlink:href="mmc-20210331.xsd#mmc_OtherReceivablesMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e05b10fa-b2c5-4371-aacf-1393b658e1f7" xlink:to="loc_mmc_OtherReceivablesMember_0f884b1e-6fa0-4961-a6c8-54e1373efcb0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_AccountsPayableandAccruedLiabilitiesandOtherLiabilitiesMember_2604847c-c2ce-4e5e-a0ad-0696fcd4b19c" xlink:href="mmc-20210331.xsd#mmc_AccountsPayableandAccruedLiabilitiesandOtherLiabilitiesMember"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e05b10fa-b2c5-4371-aacf-1393b658e1f7" xlink:to="loc_mmc_AccountsPayableandAccruedLiabilitiesandOtherLiabilitiesMember_2604847c-c2ce-4e5e-a0ad-0696fcd4b19c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_730fa357-aa41-4939-86d0-9ce31a53accb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_204e459c-5449-4222-9262-4ef1641e7cd8" xlink:to="loc_us-gaap_FinancialInstrumentAxis_730fa357-aa41-4939-86d0-9ce31a53accb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_529aba29-0d50-4f97-9d85-32ae377b5725" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FinancialInstrumentAxis_730fa357-aa41-4939-86d0-9ce31a53accb" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_529aba29-0d50-4f97-9d85-32ae377b5725" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_89b85cb2-9ebe-4cdf-b22a-e166c5548c49" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_529aba29-0d50-4f97-9d85-32ae377b5725" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_89b85cb2-9ebe-4cdf-b22a-e166c5548c49" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_e851266d-02fb-4d0b-95a7-720a910f7fcb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_529aba29-0d50-4f97-9d85-32ae377b5725" xlink:to="loc_us-gaap_MoneyMarketFundsMember_e851266d-02fb-4d0b-95a7-720a910f7fcb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_a77b7ec7-1efe-46ad-a2c2-a28363564269" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_204e459c-5449-4222-9262-4ef1641e7cd8" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_a77b7ec7-1efe-46ad-a2c2-a28363564269" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3ed2c5e1-4ae6-4db4-a066-51951b512a67" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_a77b7ec7-1efe-46ad-a2c2-a28363564269" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3ed2c5e1-4ae6-4db4-a066-51951b512a67" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_c82fa66c-4f24-4dd7-b2a5-dd7637571fba" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3ed2c5e1-4ae6-4db4-a066-51951b512a67" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_c82fa66c-4f24-4dd7-b2a5-dd7637571fba" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_a892600d-9d1b-43b1-949d-de568171be70" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3ed2c5e1-4ae6-4db4-a066-51951b512a67" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_a892600d-9d1b-43b1-949d-de568171be70" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_5279af1c-dbfe-4064-bd6b-401578e45be0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3ed2c5e1-4ae6-4db4-a066-51951b512a67" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_5279af1c-dbfe-4064-bd6b-401578e45be0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_230c6660-50bb-4226-b80f-c087f1962d4a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_204e459c-5449-4222-9262-4ef1641e7cd8" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_230c6660-50bb-4226-b80f-c087f1962d4a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_45dcff9a-9f47-47cc-934f-47b77bbbfd7b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_230c6660-50bb-4226-b80f-c087f1962d4a" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_45dcff9a-9f47-47cc-934f-47b77bbbfd7b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_ca99df50-807c-4387-9012-432d255edfb3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_45dcff9a-9f47-47cc-934f-47b77bbbfd7b" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_ca99df50-807c-4387-9012-432d255edfb3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_26d5dbdc-03d1-4056-b0ea-29ad06901a25" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_204e459c-5449-4222-9262-4ef1641e7cd8" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_26d5dbdc-03d1-4056-b0ea-29ad06901a25" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_36cab639-00a1-4b7a-b0ca-6b5bc2e57af7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_26d5dbdc-03d1-4056-b0ea-29ad06901a25" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_36cab639-00a1-4b7a-b0ca-6b5bc2e57af7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNi_42f2c106-fba0-49ce-b005-764b248db2a5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesFvNi"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_36cab639-00a1-4b7a-b0ca-6b5bc2e57af7" xlink:to="loc_us-gaap_EquitySecuritiesFvNi_42f2c106-fba0-49ce-b005-764b248db2a5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsFairValueDisclosure_e076f0eb-28d5-4cbc-9bac-8fac803c7313" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsFairValueDisclosure"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_36cab639-00a1-4b7a-b0ca-6b5bc2e57af7" xlink:to="loc_us-gaap_OtherAssetsFairValueDisclosure_e076f0eb-28d5-4cbc-9bac-8fac803c7313" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_fbb4cee1-becf-422b-b547-0b682e827306" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_36cab639-00a1-4b7a-b0ca-6b5bc2e57af7" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_fbb4cee1-becf-422b-b547-0b682e827306" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateFairValueHedgeAssetAtFairValue_25d9ec9a-2089-40ff-b3cf-c875fdecefcc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestRateFairValueHedgeAssetAtFairValue"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_36cab639-00a1-4b7a-b0ca-6b5bc2e57af7" xlink:to="loc_us-gaap_InterestRateFairValueHedgeAssetAtFairValue_25d9ec9a-2089-40ff-b3cf-c875fdecefcc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_BusinessCombinationContingentConsiderationAssetFairValueDisclosure_945edb49-e23b-4eee-9fb3-a1e5af8814a9" xlink:href="mmc-20210331.xsd#mmc_BusinessCombinationContingentConsiderationAssetFairValueDisclosure"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_36cab639-00a1-4b7a-b0ca-6b5bc2e57af7" xlink:to="loc_mmc_BusinessCombinationContingentConsiderationAssetFairValueDisclosure_945edb49-e23b-4eee-9fb3-a1e5af8814a9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_95b6bc98-358f-493c-968a-34adc4baa0ef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_36cab639-00a1-4b7a-b0ca-6b5bc2e57af7" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_95b6bc98-358f-493c-968a-34adc4baa0ef" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiduciaryAssetsAbstract_3892808e-d91d-4262-8da1-c9eca3aea889" xlink:href="mmc-20210331.xsd#mmc_FiduciaryAssetsAbstract"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_26d5dbdc-03d1-4056-b0ea-29ad06901a25" xlink:to="loc_mmc_FiduciaryAssetsAbstract_3892808e-d91d-4262-8da1-c9eca3aea889" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FiduciaryAssetsFairValueDisclosure_907ac0f1-549d-4cff-8180-7522d556c8ac" xlink:href="mmc-20210331.xsd#mmc_FiduciaryAssetsFairValueDisclosure"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_FiduciaryAssetsAbstract_3892808e-d91d-4262-8da1-c9eca3aea889" xlink:to="loc_mmc_FiduciaryAssetsFairValueDisclosure_907ac0f1-549d-4cff-8180-7522d556c8ac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_e52ee9b1-9caa-423c-a7c0-bea3a0590aaa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_26d5dbdc-03d1-4056-b0ea-29ad06901a25" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_e52ee9b1-9caa-423c-a7c0-bea3a0590aaa" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure_dfdea886-5380-4c55-a047-b4956532c092" xlink:href="mmc-20210331.xsd#mmc_BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_e52ee9b1-9caa-423c-a7c0-bea3a0590aaa" xlink:to="loc_mmc_BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure_dfdea886-5380-4c55-a047-b4956532c092" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_6f0c5172-6d32-4a81-82d9-ea518d996100" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_e52ee9b1-9caa-423c-a7c0-bea3a0590aaa" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_6f0c5172-6d32-4a81-82d9-ea518d996100" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/FairValueMeasurementsChangesInFairValueOfLevel3LiabilitiesRepresentingAcquisitionRelatedContingentConsiderationDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#FairValueMeasurementsChangesInFairValueOfLevel3LiabilitiesRepresentingAcquisitionRelatedContingentConsiderationDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/FairValueMeasurementsChangesInFairValueOfLevel3LiabilitiesRepresentingAcquisitionRelatedContingentConsiderationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosuresAbstract_e02f039e-dec7-41a2-b893-fe32affa7172" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosuresAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_538dbcc1-9573-459d-ad37-7996a350db9b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueDisclosuresAbstract_e02f039e-dec7-41a2-b893-fe32affa7172" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_538dbcc1-9573-459d-ad37-7996a350db9b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_2a0b344b-c194-4e7e-ba67-65a3b341166e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_538dbcc1-9573-459d-ad37-7996a350db9b" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_2a0b344b-c194-4e7e-ba67-65a3b341166e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_e230e3f7-2bac-463a-83fa-4d6ec34f06bf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_2a0b344b-c194-4e7e-ba67-65a3b341166e" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_e230e3f7-2bac-463a-83fa-4d6ec34f06bf" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_ContingentConsiderationMember_073c6d54-56d3-490a-a144-f4bea27e5a50" xlink:href="mmc-20210331.xsd#mmc_ContingentConsiderationMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_e230e3f7-2bac-463a-83fa-4d6ec34f06bf" xlink:to="loc_mmc_ContingentConsiderationMember_073c6d54-56d3-490a-a144-f4bea27e5a50" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_f14c6521-8b57-4738-874b-6d4ea39b7b81" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_538dbcc1-9573-459d-ad37-7996a350db9b" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_f14c6521-8b57-4738-874b-6d4ea39b7b81" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_05a0d526-04da-4fc7-a987-ccf2487ada63" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_f14c6521-8b57-4738-874b-6d4ea39b7b81" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_05a0d526-04da-4fc7-a987-ccf2487ada63" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_7e40446c-9b9e-4f0a-969a-ee9e56479e8b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_05a0d526-04da-4fc7-a987-ccf2487ada63" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_7e40446c-9b9e-4f0a-969a-ee9e56479e8b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_824b7e39-acc4-4ad9-80aa-9cc2824121ab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_05a0d526-04da-4fc7-a987-ccf2487ada63" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_824b7e39-acc4-4ad9-80aa-9cc2824121ab" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_3f733f46-182f-4fdb-a87a-1567dc9e41f0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_05a0d526-04da-4fc7-a987-ccf2487ada63" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_3f733f46-182f-4fdb-a87a-1567dc9e41f0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_8b610f25-91e8-42c1-ac8d-a1314594f5fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_05a0d526-04da-4fc7-a987-ccf2487ada63" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_8b610f25-91e8-42c1-ac8d-a1314594f5fd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityOtherAdjustments_26d582c2-39f7-40a1-af56-eb91e5000c81" xlink:href="mmc-20210331.xsd#mmc_FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityOtherAdjustments"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_05a0d526-04da-4fc7-a987-ccf2487ada63" xlink:to="loc_mmc_FairValueMeasurementwithUnobservableInputsReconciliationRecurringBasisLiabilityOtherAdjustments_26d582c2-39f7-40a1-af56-eb91e5000c81" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_0e5dcb2f-04b5-4518-a1e0-c502803dbbfb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_05a0d526-04da-4fc7-a987-ccf2487ada63" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_0e5dcb2f-04b5-4518-a1e0-c502803dbbfb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/Derivatives" xlink:type="simple" xlink:href="mmc-20210331.xsd#Derivatives"/>
  <link:presentationLink xlink:role="http://mmc.com/role/Derivatives" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_ab651023-e170-4d87-b3df-e691193138d1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_b753b9d5-d708-4bb9-a59c-44db45f0b2ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_ab651023-e170-4d87-b3df-e691193138d1" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_b753b9d5-d708-4bb9-a59c-44db45f0b2ac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/DerivativesNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#DerivativesNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/DerivativesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_99c580d2-3a82-438a-b391-01208ae24e4f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_fc3d97f3-776b-4350-bf60-d55b534d7aa4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_99c580d2-3a82-438a-b391-01208ae24e4f" xlink:to="loc_us-gaap_DerivativeTable_fc3d97f3-776b-4350-bf60-d55b534d7aa4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_262568a0-4efe-46e1-8ac7-f7d227d94347" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DerivativeTable_fc3d97f3-776b-4350-bf60-d55b534d7aa4" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_262568a0-4efe-46e1-8ac7-f7d227d94347" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_7f49b8b5-bd01-4a17-a22e-bd2129dddb0b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_262568a0-4efe-46e1-8ac7-f7d227d94347" xlink:to="loc_us-gaap_HedgingRelationshipDomain_7f49b8b5-bd01-4a17-a22e-bd2129dddb0b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentHedgingMember_25b27a5f-1e34-4bea-ad5e-36b5cc7ebb73" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetInvestmentHedgingMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_HedgingRelationshipDomain_7f49b8b5-bd01-4a17-a22e-bd2129dddb0b" xlink:to="loc_us-gaap_NetInvestmentHedgingMember_25b27a5f-1e34-4bea-ad5e-36b5cc7ebb73" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_4c702e0f-88ff-43e2-8d02-a8fad5064101" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DerivativeTable_fc3d97f3-776b-4350-bf60-d55b534d7aa4" xlink:to="loc_us-gaap_DerivativeLineItems_4c702e0f-88ff-43e2-8d02-a8fad5064101" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_6abd7b9c-9ed9-41ac-8888-2ba5279634e7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DerivativeLineItems_4c702e0f-88ff-43e2-8d02-a8fad5064101" xlink:to="loc_us-gaap_DerivativeNotionalAmount_6abd7b9c-9ed9-41ac-8888-2ba5279634e7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_NetInvestmentHedgeThresholdPercentageoftheEquityBalance_573809d4-688b-44d1-9983-f052a0f1d869" xlink:href="mmc-20210331.xsd#mmc_NetInvestmentHedgeThresholdPercentageoftheEquityBalance"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DerivativeLineItems_4c702e0f-88ff-43e2-8d02-a8fad5064101" xlink:to="loc_mmc_NetInvestmentHedgeThresholdPercentageoftheEquityBalance_573809d4-688b-44d1-9983-f052a0f1d869" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax_6af4bc2e-2389-40b3-94ae-2ce865523d8f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DerivativeLineItems_4c702e0f-88ff-43e2-8d02-a8fad5064101" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax_6af4bc2e-2389-40b3-94ae-2ce865523d8f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/Leases" xlink:type="simple" xlink:href="mmc-20210331.xsd#Leases"/>
  <link:presentationLink xlink:role="http://mmc.com/role/Leases" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAbstract_1814d515-2f5e-4763-a5bb-e765440a053b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeasesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeasesTextBlock_d030d9c9-a731-4199-88c9-4c80027216ac" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeasesTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_1814d515-2f5e-4763-a5bb-e765440a053b" xlink:to="loc_us-gaap_LesseeOperatingLeasesTextBlock_d030d9c9-a731-4199-88c9-4c80027216ac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/LeasesTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#LeasesTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/LeasesTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAbstract_0d9b0400-1fd0-4306-a3dc-20c45540d5e0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeasesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseCostTableTextBlock_f2794789-9b88-4004-b9da-cf671f6283e4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseCostTableTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_0d9b0400-1fd0-4306-a3dc-20c45540d5e0" xlink:to="loc_us-gaap_LeaseCostTableTextBlock_f2794789-9b88-4004-b9da-cf671f6283e4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_6413c789-1485-424b-8bc0-15e539cb315d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_0d9b0400-1fd0-4306-a3dc-20c45540d5e0" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_6413c789-1485-424b-8bc0-15e539cb315d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/LeasesNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#LeasesNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/LeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAbstract_d3252ecc-0017-429d-9f61-c7d2d8f0b9ae" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeasesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_ef272d5b-1771-4f8d-8ef7-c58f3d2ed076" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d3252ecc-0017-429d-9f61-c7d2d8f0b9ae" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_ef272d5b-1771-4f8d-8ef7-c58f3d2ed076" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_ed2e0610-2381-4b4c-9ddb-4acb917e1710" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_ef272d5b-1771-4f8d-8ef7-c58f3d2ed076" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_ed2e0610-2381-4b4c-9ddb-4acb917e1710" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_ec1a3af4-1b89-488a-b005-20a251007c54" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_ed2e0610-2381-4b4c-9ddb-4acb917e1710" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_ec1a3af4-1b89-488a-b005-20a251007c54" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OfficeBuildingMember_15a56927-85ba-4ae6-8501-6f50255be5f4" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_OfficeBuildingMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_ec1a3af4-1b89-488a-b005-20a251007c54" xlink:to="loc_srt_OfficeBuildingMember_15a56927-85ba-4ae6-8501-6f50255be5f4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_c7933440-cdc2-42dd-8aa0-6869ec34911e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_ef272d5b-1771-4f8d-8ef7-c58f3d2ed076" xlink:to="loc_srt_RangeAxis_c7933440-cdc2-42dd-8aa0-6869ec34911e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_911d8cd4-94f9-45ae-8edc-aa05c7d4af2f" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeAxis_c7933440-cdc2-42dd-8aa0-6869ec34911e" xlink:to="loc_srt_RangeMember_911d8cd4-94f9-45ae-8edc-aa05c7d4af2f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_c407969d-41c2-4b21-9be7-c2971fb849c0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeMember_911d8cd4-94f9-45ae-8edc-aa05c7d4af2f" xlink:to="loc_srt_MinimumMember_c407969d-41c2-4b21-9be7-c2971fb849c0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_a2443732-486f-4f38-a4eb-db1113e00003" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_RangeMember_911d8cd4-94f9-45ae-8edc-aa05c7d4af2f" xlink:to="loc_srt_MaximumMember_a2443732-486f-4f38-a4eb-db1113e00003" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_1d3d02a4-566a-4051-b851-67af17447b12" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_ef272d5b-1771-4f8d-8ef7-c58f3d2ed076" xlink:to="loc_us-gaap_LesseeLeaseDescriptionLineItems_1d3d02a4-566a-4051-b851-67af17447b12" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_685674fe-0466-481a-994c-ea01a912219c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_1d3d02a4-566a-4051-b851-67af17447b12" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_685674fe-0466-481a-994c-ea01a912219c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_LeaseObligationsPercent_6e642638-027a-42d1-b42d-fa4c15ed721d" xlink:href="mmc-20210331.xsd#mmc_LeaseObligationsPercent"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_1d3d02a4-566a-4051-b851-67af17447b12" xlink:to="loc_mmc_LeaseObligationsPercent_6e642638-027a-42d1-b42d-fa4c15ed721d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/LeasesLeaseCostandAdditionalInformationDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#LeasesLeaseCostandAdditionalInformationDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/LeasesLeaseCostandAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAbstract_2b5afb42-05bf-46fd-8a8f-cf115822adab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeasesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_28e3495c-1763-471c-b332-2bcb83692aed" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_2b5afb42-05bf-46fd-8a8f-cf115822adab" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_28e3495c-1763-471c-b332-2bcb83692aed" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4b653aac-225b-4175-9111-862269854fb9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_28e3495c-1763-471c-b332-2bcb83692aed" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4b653aac-225b-4175-9111-862269854fb9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f76caebc-8591-4c88-9d35-1b247824a73b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_4b653aac-225b-4175-9111-862269854fb9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f76caebc-8591-4c88-9d35-1b247824a73b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_RealEstateLeaseMember_e8568123-7774-4f9f-ac05-93e03d0a1bb9" xlink:href="mmc-20210331.xsd#mmc_RealEstateLeaseMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_f76caebc-8591-4c88-9d35-1b247824a73b" xlink:to="loc_mmc_RealEstateLeaseMember_e8568123-7774-4f9f-ac05-93e03d0a1bb9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_28e3495c-1763-471c-b332-2bcb83692aed" xlink:to="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseCost_6c5f8cc0-59fe-460e-a4e4-d98c620cf5e1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseCost"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:to="loc_us-gaap_OperatingLeaseCost_6c5f8cc0-59fe-460e-a4e4-d98c620cf5e1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermLeaseCost_9d720e85-2009-4b68-ba8f-7e917fd11cce" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermLeaseCost"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:to="loc_us-gaap_ShortTermLeaseCost_9d720e85-2009-4b68-ba8f-7e917fd11cce" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableLeaseCost_f8f8c0e0-8b9f-4011-9414-c8de7cbf562d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableLeaseCost"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:to="loc_us-gaap_VariableLeaseCost_f8f8c0e0-8b9f-4011-9414-c8de7cbf562d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubleaseIncome_15bdc209-57a9-4dde-be91-5d384618cf0b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubleaseIncome"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:to="loc_us-gaap_SubleaseIncome_15bdc209-57a9-4dde-be91-5d384618cf0b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseCost_8f1b2bcb-0774-478f-86f1-8e582a71d456" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseCost"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:to="loc_us-gaap_LeaseCost_8f1b2bcb-0774-478f-86f1-8e582a71d456" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeasePayments_d9a73312-aa83-4a3c-acf8-89f631839e85" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasePayments"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:to="loc_us-gaap_OperatingLeasePayments_d9a73312-aa83-4a3c-acf8-89f631839e85" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_bbae2b72-9407-4eac-a035-eadb8b3f171b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_bbae2b72-9407-4eac-a035-eadb8b3f171b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_bad3cd1f-506c-43c4-b4ab-e8864baba7a6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_bad3cd1f-506c-43c4-b4ab-e8864baba7a6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_6a2e03f6-ebbd-4d97-9f39-617d68a6e2dc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_fcaa8536-b34a-457d-8c7b-f1cbfec8c8a0" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_6a2e03f6-ebbd-4d97-9f39-617d68a6e2dc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/LeasesFutureMinimumPaymentsforOperatingLeasesDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#LeasesFutureMinimumPaymentsforOperatingLeasesDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/LeasesFutureMinimumPaymentsforOperatingLeasesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeasesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_778abc31-3d13-47fb-a33c-b35faba9dd6b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_778abc31-3d13-47fb-a33c-b35faba9dd6b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_b009a6aa-bd61-49f5-874d-2c91131f8714" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_b009a6aa-bd61-49f5-874d-2c91131f8714" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_bcee9482-1d30-432c-9a78-eba6db5ecb90" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_bcee9482-1d30-432c-9a78-eba6db5ecb90" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_31d63919-d345-4a91-9ad1-2f618173049b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_31d63919-d345-4a91-9ad1-2f618173049b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_d5833415-2fe0-4292-92fb-0653845e7e60" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_d5833415-2fe0-4292-92fb-0653845e7e60" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_c74f237a-8dac-478a-8da1-8a05bf7f3572" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_c74f237a-8dac-478a-8da1-8a05bf7f3572" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_67dc13ca-f5f0-4b9a-9fe2-4d2fcfcb99a7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_67dc13ca-f5f0-4b9a-9fe2-4d2fcfcb99a7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_8787010a-95a5-4dca-ade1-b51a83e43599" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_8787010a-95a5-4dca-ade1-b51a83e43599" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_2ccdec05-2cde-49e9-a4cb-126100e2d03c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_2ccdec05-2cde-49e9-a4cb-126100e2d03c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_dfb3bc70-c9da-4cae-9499-83288d330d6b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_OperatingLeaseLiability_dfb3bc70-c9da-4cae-9499-83288d330d6b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_ea68a96c-e00c-4941-8a02-0818676d22cf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_ea68a96c-e00c-4941-8a02-0818676d22cf" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_741a5589-dcb5-4880-82e0-372f5f65add7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LeasesAbstract_d61ee2d2-c112-444f-a106-d6d5e8c4cdc2" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_741a5589-dcb5-4880-82e0-372f5f65add7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/LeasesFutureMinimumPaymentsforOperatingLeasesDetails_1" xlink:type="simple" xlink:href="mmc-20210331.xsd#LeasesFutureMinimumPaymentsforOperatingLeasesDetails_1"/>
  <link:presentationLink xlink:role="http://mmc.com/role/LeasesFutureMinimumPaymentsforOperatingLeasesDetails_1" xlink:type="extended"/>
  <link:roleRef roleURI="http://mmc.com/role/RetirementBenefits" xlink:type="simple" xlink:href="mmc-20210331.xsd#RetirementBenefits"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RetirementBenefits" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_16b6989d-235c-48f8-8fe2-685a6dc29af3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CompensationAndRetirementDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock_05a80c6e-69ca-402c-b3ff-d566cb64e4f0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_16b6989d-235c-48f8-8fe2-685a6dc29af3" xlink:to="loc_us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock_05a80c6e-69ca-402c-b3ff-d566cb64e4f0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RetirementBenefitsTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#RetirementBenefitsTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RetirementBenefitsTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_8f027ea0-1f25-47ff-b065-3eef6c7f226b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CompensationAndRetirementDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfNetBenefitCostsTableTextBlock_2a0c1b48-257a-4a6d-bd8e-36dca2e7675f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfNetBenefitCostsTableTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_8f027ea0-1f25-47ff-b065-3eef6c7f226b" xlink:to="loc_us-gaap_ScheduleOfNetBenefitCostsTableTextBlock_2a0c1b48-257a-4a6d-bd8e-36dca2e7675f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAssumptionsUsedTableTextBlock_3a6dc550-6346-4bbf-b9ca-1d215bef791e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAssumptionsUsedTableTextBlock"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_8f027ea0-1f25-47ff-b065-3eef6c7f226b" xlink:to="loc_us-gaap_ScheduleOfAssumptionsUsedTableTextBlock_3a6dc550-6346-4bbf-b9ca-1d215bef791e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RetirementBenefitsNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RetirementBenefitsNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RetirementBenefitsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_71b7c83e-a551-4f67-824e-4cc321a5e6b0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CompensationAndRetirementDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_f4c26c98-752a-4746-afc8-e9ef88271795" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_71b7c83e-a551-4f67-824e-4cc321a5e6b0" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_f4c26c98-752a-4746-afc8-e9ef88271795" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_d5efea0c-189b-4f76-bd29-8e9ff6f1f58b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_f4c26c98-752a-4746-afc8-e9ef88271795" xlink:to="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_d5efea0c-189b-4f76-bd29-8e9ff6f1f58b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanAssetCategoriesDomain_4f0badcd-32b3-4d7f-a555-14aee803eac1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanAssetCategoriesDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis_d5efea0c-189b-4f76-bd29-8e9ff6f1f58b" xlink:to="loc_us-gaap_PlanAssetCategoriesDomain_4f0badcd-32b3-4d7f-a555-14aee803eac1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityFundsMember_77858569-235f-461f-8340-3cccc6646f7c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityFundsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_4f0badcd-32b3-4d7f-a555-14aee803eac1" xlink:to="loc_us-gaap_EquityFundsMember_77858569-235f-461f-8340-3cccc6646f7c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedIncomeFundsMember_172f1e09-2659-4a80-8dfc-ef55206f5fa2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FixedIncomeFundsMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_PlanAssetCategoriesDomain_4f0badcd-32b3-4d7f-a555-14aee803eac1" xlink:to="loc_us-gaap_FixedIncomeFundsMember_172f1e09-2659-4a80-8dfc-ef55206f5fa2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanSponsorLocationAxis_7844b395-ab93-4c33-a522-7daf4e0745ee" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanSponsorLocationAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_f4c26c98-752a-4746-afc8-e9ef88271795" xlink:to="loc_us-gaap_RetirementPlanSponsorLocationAxis_7844b395-ab93-4c33-a522-7daf4e0745ee" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanSponsorLocationDomain_c6149477-2072-4fdd-9e52-fdc5f6290c44" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanSponsorLocationDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanSponsorLocationAxis_7844b395-ab93-4c33-a522-7daf4e0745ee" xlink:to="loc_us-gaap_RetirementPlanSponsorLocationDomain_c6149477-2072-4fdd-9e52-fdc5f6290c44" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DomesticPlanMember_0b6f479e-905a-4927-95fa-ef32569152e3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DomesticPlanMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanSponsorLocationDomain_c6149477-2072-4fdd-9e52-fdc5f6290c44" xlink:to="loc_us-gaap_DomesticPlanMember_0b6f479e-905a-4927-95fa-ef32569152e3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_a027120e-3fbb-4bba-b14b-5d21344df261" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_US"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DomesticPlanMember_0b6f479e-905a-4927-95fa-ef32569152e3" xlink:to="loc_country_US_a027120e-3fbb-4bba-b14b-5d21344df261" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignPlanMember_bd9a2c66-1719-408e-adfe-38530518b88a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignPlanMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanSponsorLocationDomain_c6149477-2072-4fdd-9e52-fdc5f6290c44" xlink:to="loc_us-gaap_ForeignPlanMember_bd9a2c66-1719-408e-adfe-38530518b88a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_GB_10bb977d-54b1-4ebb-b980-127dedf96d2c" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_GB"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ForeignPlanMember_bd9a2c66-1719-408e-adfe-38530518b88a" xlink:to="loc_country_GB_10bb977d-54b1-4ebb-b980-127dedf96d2c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_853b0bc4-9d5e-4d89-860f-2d4809f4aa32" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_f4c26c98-752a-4746-afc8-e9ef88271795" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_853b0bc4-9d5e-4d89-860f-2d4809f4aa32" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_1699ebe7-5ba1-482f-a661-986af040f731" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_853b0bc4-9d5e-4d89-860f-2d4809f4aa32" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_1699ebe7-5ba1-482f-a661-986af040f731" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_acbd0253-4f37-4efc-8c27-339a55a9faf3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_1699ebe7-5ba1-482f-a661-986af040f731" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_acbd0253-4f37-4efc-8c27-339a55a9faf3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_a597bbea-a68b-426f-846c-0ab167d321fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_f4c26c98-752a-4746-afc8-e9ef88271795" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_a597bbea-a68b-426f-846c-0ab167d321fd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_205fc37b-bf7d-47be-9efc-2e25f2fea0c9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_a597bbea-a68b-426f-846c-0ab167d321fd" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_205fc37b-bf7d-47be-9efc-2e25f2fea0c9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_UnitedKingdomPensionandPostretirementBenefitPlanDefinedBenefitMember_5a5f40c9-5eea-44f3-a196-6c3e2d95fe05" xlink:href="mmc-20210331.xsd#mmc_UnitedKingdomPensionandPostretirementBenefitPlanDefinedBenefitMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_205fc37b-bf7d-47be-9efc-2e25f2fea0c9" xlink:to="loc_mmc_UnitedKingdomPensionandPostretirementBenefitPlanDefinedBenefitMember_5a5f40c9-5eea-44f3-a196-6c3e2d95fe05" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_0371539a-9676-4758-91f2-8756fb78a651" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_f4c26c98-752a-4746-afc8-e9ef88271795" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_0371539a-9676-4758-91f2-8756fb78a651" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_9d5a5a52-cadb-4ed0-959a-331cc350ab5d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_0371539a-9676-4758-91f2-8756fb78a651" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_9d5a5a52-cadb-4ed0-959a-331cc350ab5d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_ae78ca3e-5071-4b88-a241-2698cc0a38fb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeographicConcentrationRiskMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_9d5a5a52-cadb-4ed0-959a-331cc350ab5d" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_ae78ca3e-5071-4b88-a241-2698cc0a38fb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_162db1f1-2d05-4a7e-830d-74c8e83c5a99" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_f4c26c98-752a-4746-afc8-e9ef88271795" xlink:to="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_162db1f1-2d05-4a7e-830d-74c8e83c5a99" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage_a34f0747-4a99-49db-88d2-aa3995bfa6af" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_162db1f1-2d05-4a7e-830d-74c8e83c5a99" xlink:to="loc_us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage_a34f0747-4a99-49db-88d2-aa3995bfa6af" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations_822a9680-282f-4d3c-bc05-331f7254c4fb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_162db1f1-2d05-4a7e-830d-74c8e83c5a99" xlink:to="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations_822a9680-282f-4d3c-bc05-331f7254c4fb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_2750e286-8abb-4698-b928-670685e2c83b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_162db1f1-2d05-4a7e-830d-74c8e83c5a99" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_2750e286-8abb-4698-b928-670685e2c83b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_5f31477b-a190-43eb-bcc1-4d2f130e20d8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanContributionsByEmployer"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_162db1f1-2d05-4a7e-830d-74c8e83c5a99" xlink:to="loc_us-gaap_DefinedBenefitPlanContributionsByEmployer_5f31477b-a190-43eb-bcc1-4d2f130e20d8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsRemainderOfFiscalYear_a2e28b2a-47bc-440c-b453-c5b978b6b178" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsRemainderOfFiscalYear"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_162db1f1-2d05-4a7e-830d-74c8e83c5a99" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsRemainderOfFiscalYear_a2e28b2a-47bc-440c-b453-c5b978b6b178" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanCostRecognized_726c3a46-597e-44ab-a7a8-2599b6f1012f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedContributionPlanCostRecognized"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_162db1f1-2d05-4a7e-830d-74c8e83c5a99" xlink:to="loc_us-gaap_DefinedContributionPlanCostRecognized_726c3a46-597e-44ab-a7a8-2599b6f1012f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RetirementBenefitsScheduleOfDefinedBenefitPlanNetPeriodicBenefitCostCombinedUSandSignificantNonUSPlansDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RetirementBenefitsScheduleOfDefinedBenefitPlanNetPeriodicBenefitCostCombinedUSandSignificantNonUSPlansDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RetirementBenefitsScheduleOfDefinedBenefitPlanNetPeriodicBenefitCostCombinedUSandSignificantNonUSPlansDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_57998622-064c-4fb8-b18c-f99b27a64e14" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CompensationAndRetirementDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_17078c67-48b8-42ca-80ef-9ae07f8c5fbc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_57998622-064c-4fb8-b18c-f99b27a64e14" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_17078c67-48b8-42ca-80ef-9ae07f8c5fbc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_76a27d2a-df3f-4781-a88a-7e650bfd60e5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_17078c67-48b8-42ca-80ef-9ae07f8c5fbc" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_76a27d2a-df3f-4781-a88a-7e650bfd60e5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_30b8b161-5f53-450b-8dd8-d4743e42e375" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_76a27d2a-df3f-4781-a88a-7e650bfd60e5" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_30b8b161-5f53-450b-8dd8-d4743e42e375" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_50c37c67-3105-4861-a3dd-95e10c6728d9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_30b8b161-5f53-450b-8dd8-d4743e42e375" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_50c37c67-3105-4861-a3dd-95e10c6728d9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_c4450074-5f38-4298-823d-a9e65ce54d1c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_30b8b161-5f53-450b-8dd8-d4743e42e375" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_c4450074-5f38-4298-823d-a9e65ce54d1c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanSponsorLocationAxis_cff4a459-3f2d-4b3d-873b-abf936a7b12c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanSponsorLocationAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_17078c67-48b8-42ca-80ef-9ae07f8c5fbc" xlink:to="loc_us-gaap_RetirementPlanSponsorLocationAxis_cff4a459-3f2d-4b3d-873b-abf936a7b12c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanSponsorLocationDomain_78de1169-6402-4ebc-9a18-1731edf8996f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanSponsorLocationDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanSponsorLocationAxis_cff4a459-3f2d-4b3d-873b-abf936a7b12c" xlink:to="loc_us-gaap_RetirementPlanSponsorLocationDomain_78de1169-6402-4ebc-9a18-1731edf8996f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DomesticPlanMember_99a3a71c-f3e2-4037-a357-6c69861d8257" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DomesticPlanMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanSponsorLocationDomain_78de1169-6402-4ebc-9a18-1731edf8996f" xlink:to="loc_us-gaap_DomesticPlanMember_99a3a71c-f3e2-4037-a357-6c69861d8257" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_c82fac0a-943a-4e05-b711-a59e94950814" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_US"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DomesticPlanMember_99a3a71c-f3e2-4037-a357-6c69861d8257" xlink:to="loc_country_US_c82fac0a-943a-4e05-b711-a59e94950814" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignPlanMember_4ebdc16d-cbe0-4a52-8b9d-ea3d69b2633d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignPlanMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanSponsorLocationDomain_78de1169-6402-4ebc-9a18-1731edf8996f" xlink:to="loc_us-gaap_ForeignPlanMember_4ebdc16d-cbe0-4a52-8b9d-ea3d69b2633d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_b08abe53-c3a5-4199-8785-363100c2e8ff" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_17078c67-48b8-42ca-80ef-9ae07f8c5fbc" xlink:to="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_b08abe53-c3a5-4199-8785-363100c2e8ff" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_df15ae65-480f-49d7-86fb-d8cfff892e5d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanServiceCost"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_b08abe53-c3a5-4199-8785-363100c2e8ff" xlink:to="loc_us-gaap_DefinedBenefitPlanServiceCost_df15ae65-480f-49d7-86fb-d8cfff892e5d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_14b18ec3-96cf-44ec-bff2-784c82030199" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_b08abe53-c3a5-4199-8785-363100c2e8ff" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_14b18ec3-96cf-44ec-bff2-784c82030199" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_e5138af4-72e1-418a-9ca6-d88323ed77bc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_b08abe53-c3a5-4199-8785-363100c2e8ff" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_e5138af4-72e1-418a-9ca6-d88323ed77bc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_50572248-11fb-44d4-a096-51934f06b177" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_b08abe53-c3a5-4199-8785-363100c2e8ff" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_50572248-11fb-44d4-a096-51934f06b177" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_22598bd4-a73a-43d1-ba99-9afc811a6226" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_b08abe53-c3a5-4199-8785-363100c2e8ff" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_22598bd4-a73a-43d1-ba99-9afc811a6226" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations_afcf1aa0-03cc-4fb3-8a34-f58cf9986485" xlink:href="mmc-20210331.xsd#mmc_DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_b08abe53-c3a5-4199-8785-363100c2e8ff" xlink:to="loc_mmc_DefinedBenefitPlanNetPeriodicBenefitCostExcludingCurtailmentsSettlementsandPlanTerminations_afcf1aa0-03cc-4fb3-8a34-f58cf9986485" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_92dc2ba9-639a-427e-955f-9919e596de59" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_b08abe53-c3a5-4199-8785-363100c2e8ff" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_92dc2ba9-639a-427e-955f-9919e596de59" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RetirementBenefitsScheduleOfDefinedBenefitPlanNetPeriodicBenefitCostAmountsRecordedinConsolidatedStatementofIncomeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RetirementBenefitsScheduleOfDefinedBenefitPlanNetPeriodicBenefitCostAmountsRecordedinConsolidatedStatementofIncomeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RetirementBenefitsScheduleOfDefinedBenefitPlanNetPeriodicBenefitCostAmountsRecordedinConsolidatedStatementofIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_ea5e5af7-8999-4713-ad20-837cc58680b5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CompensationAndRetirementDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_869470ba-4d1b-4396-a8a8-7b64659e4b62" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_ea5e5af7-8999-4713-ad20-837cc58680b5" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_869470ba-4d1b-4396-a8a8-7b64659e4b62" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_5127e0ec-1914-4249-95c5-584b87346241" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_869470ba-4d1b-4396-a8a8-7b64659e4b62" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_5127e0ec-1914-4249-95c5-584b87346241" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_c351bfd0-4230-460e-a58d-77702322c41e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_5127e0ec-1914-4249-95c5-584b87346241" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_c351bfd0-4230-460e-a58d-77702322c41e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_03ea71a3-abf8-4d64-b4e9-98e685807d66" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_c351bfd0-4230-460e-a58d-77702322c41e" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_03ea71a3-abf8-4d64-b4e9-98e685807d66" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_9f66acf5-0828-4d71-a587-12ba9d15f633" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_c351bfd0-4230-460e-a58d-77702322c41e" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_9f66acf5-0828-4d71-a587-12ba9d15f633" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_9018ffce-8e2f-4d21-a92c-ab0a64c0dca5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_869470ba-4d1b-4396-a8a8-7b64659e4b62" xlink:to="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_9018ffce-8e2f-4d21-a92c-ab0a64c0dca5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_d0211980-e909-4917-b16b-203f20a4632e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_9018ffce-8e2f-4d21-a92c-ab0a64c0dca5" xlink:to="loc_us-gaap_OperatingIncomeLoss_d0211980-e909-4917-b16b-203f20a4632e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanOtherCosts_d5bf188c-1bcb-4817-b3c8-00e5caa93a64" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanOtherCosts"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_9018ffce-8e2f-4d21-a92c-ab0a64c0dca5" xlink:to="loc_us-gaap_DefinedBenefitPlanOtherCosts_d5bf188c-1bcb-4817-b3c8-00e5caa93a64" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_9bad531b-0293-4ad0-a7ac-972f2b333cb2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_9018ffce-8e2f-4d21-a92c-ab0a64c0dca5" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_9bad531b-0293-4ad0-a7ac-972f2b333cb2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RetirementBenefitsScheduleOfDefinedBenefitPlanWeightedAverageAssumptionUsedInCalculatingNetPeriodicBenefitCostDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RetirementBenefitsScheduleOfDefinedBenefitPlanWeightedAverageAssumptionUsedInCalculatingNetPeriodicBenefitCostDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RetirementBenefitsScheduleOfDefinedBenefitPlanWeightedAverageAssumptionUsedInCalculatingNetPeriodicBenefitCostDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_9a69330c-7e7a-4cbc-af78-b85848296915" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CompensationAndRetirementDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_97b8eeb1-2e2f-4b92-9833-35939dc68a35" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CompensationAndRetirementDisclosureAbstract_9a69330c-7e7a-4cbc-af78-b85848296915" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_97b8eeb1-2e2f-4b92-9833-35939dc68a35" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_08176a9d-1b27-4651-bcdc-9fae4fad443d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_97b8eeb1-2e2f-4b92-9833-35939dc68a35" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_08176a9d-1b27-4651-bcdc-9fae4fad443d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_a033e289-59de-4504-8b26-116ea230a54b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_08176a9d-1b27-4651-bcdc-9fae4fad443d" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_a033e289-59de-4504-8b26-116ea230a54b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionPlansDefinedBenefitMember_1e86177a-d5de-4881-a76b-b9e5c6b411bd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_a033e289-59de-4504-8b26-116ea230a54b" xlink:to="loc_us-gaap_PensionPlansDefinedBenefitMember_1e86177a-d5de-4881-a76b-b9e5c6b411bd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_9c3e8b8e-2e72-49c1-8dff-8bab998f588d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_a033e289-59de-4504-8b26-116ea230a54b" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_9c3e8b8e-2e72-49c1-8dff-8bab998f588d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_3b9c452b-b559-4ee5-8b48-72be7c5b9d86" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_97b8eeb1-2e2f-4b92-9833-35939dc68a35" xlink:to="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_3b9c452b-b559-4ee5-8b48-72be7c5b9d86" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_06f2cbc4-256e-4a4a-aeb8-fbd75dd1c661" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_3b9c452b-b559-4ee5-8b48-72be7c5b9d86" xlink:to="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_06f2cbc4-256e-4a4a-aeb8-fbd75dd1c661" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets_64d6d5e4-78ef-4079-a438-909c1ef888f4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_06f2cbc4-256e-4a4a-aeb8-fbd75dd1c661" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets_64d6d5e4-78ef-4079-a438-909c1ef888f4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate_42a171ed-856d-451a-b5bc-620434e8c92c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_06f2cbc4-256e-4a4a-aeb8-fbd75dd1c661" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate_42a171ed-856d-451a-b5bc-620434e8c92c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease_13e98c6f-2c09-403a-9896-623b2cd0613a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DefinedBenefitPlanWeightedAverageAssumptionsUsedInCalculatingNetPeriodicBenefitCostAbstract_06f2cbc4-256e-4a4a-aeb8-fbd75dd1c661" xlink:to="loc_us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease_13e98c6f-2c09-403a-9896-623b2cd0613a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/Debt" xlink:type="simple" xlink:href="mmc-20210331.xsd#Debt"/>
  <link:presentationLink xlink:role="http://mmc.com/role/Debt" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtDisclosureAbstract_eb19f581-8200-417e-9b9e-ad997d8ab3cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtDisclosureTextBlock_9b694def-4629-43df-8add-b308dc6f5560" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtDisclosureTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtDisclosureAbstract_eb19f581-8200-417e-9b9e-ad997d8ab3cb" xlink:to="loc_us-gaap_DebtDisclosureTextBlock_9b694def-4629-43df-8add-b308dc6f5560" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/DebtTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#DebtTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/DebtTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtDisclosureAbstract_ce04aadd-5bdb-4f6a-becb-2b756e10a4d1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDebtInstrumentsTextBlock_bd7a2a4d-7ffd-4d90-a0b5-ac83c46df269" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfDebtInstrumentsTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtDisclosureAbstract_ce04aadd-5bdb-4f6a-becb-2b756e10a4d1" xlink:to="loc_us-gaap_ScheduleOfDebtInstrumentsTextBlock_bd7a2a4d-7ffd-4d90-a0b5-ac83c46df269" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock_317340f5-dddc-4388-b37c-4d7d2d1925b8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtDisclosureAbstract_ce04aadd-5bdb-4f6a-becb-2b756e10a4d1" xlink:to="loc_us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock_317340f5-dddc-4388-b37c-4d7d2d1925b8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/DebtScheduleOfOutstandingDebtDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#DebtScheduleOfOutstandingDebtDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/DebtScheduleOfOutstandingDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtDisclosureAbstract_7849232c-d05e-475e-b647-691e52ee0f0e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_0f5f8e28-6e69-4ad4-9ae4-f5271229acf9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtDisclosureAbstract_7849232c-d05e-475e-b647-691e52ee0f0e" xlink:to="loc_us-gaap_DebtInstrumentTable_0f5f8e28-6e69-4ad4-9ae4-f5271229acf9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_05f0d3ec-bf3c-4dae-9bcc-c203a0b2b3be" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentTable_0f5f8e28-6e69-4ad4-9ae4-f5271229acf9" xlink:to="loc_us-gaap_DebtInstrumentAxis_05f0d3ec-bf3c-4dae-9bcc-c203a0b2b3be" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentAxis_05f0d3ec-bf3c-4dae-9bcc-c203a0b2b3be" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_SeniorDebtObligationsDue2021Member_86e4f56d-ae9d-4e65-a336-0830ab3f99ff" xlink:href="mmc-20210331.xsd#mmc_SeniorDebtObligationsDue2021Member"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_SeniorDebtObligationsDue2021Member_86e4f56d-ae9d-4e65-a336-0830ab3f99ff" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_SeniorDebtObligationsDue2022Member_a9074215-8a71-4c64-99b2-5528e96329be" xlink:href="mmc-20210331.xsd#mmc_SeniorDebtObligationsDue2022Member"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_SeniorDebtObligationsDue2022Member_a9074215-8a71-4c64-99b2-5528e96329be" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_SeniorDebtObligations3.30Due2023Member_fd28c965-e03c-4f77-86f0-54a3c72270e2" xlink:href="mmc-20210331.xsd#mmc_SeniorDebtObligations3.30Due2023Member"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_SeniorDebtObligations3.30Due2023Member_fd28c965-e03c-4f77-86f0-54a3c72270e2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A4.05SeniorDebtObligationsDue2023Member_cc140089-9bfa-4fd2-af28-56d648a50ca3" xlink:href="mmc-20210331.xsd#mmc_A4.05SeniorDebtObligationsDue2023Member"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_A4.05SeniorDebtObligationsDue2023Member_cc140089-9bfa-4fd2-af28-56d648a50ca3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_SeniorDebtObligationsDue2024Member_bae26c6e-a3fc-4840-8142-4279f3a43561" xlink:href="mmc-20210331.xsd#mmc_SeniorDebtObligationsDue2024Member"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_SeniorDebtObligationsDue2024Member_bae26c6e-a3fc-4840-8142-4279f3a43561" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A3.875SeniorDebtObligationsDue2024Member_6e93c029-a5a8-41be-84e4-00625f51ce11" xlink:href="mmc-20210331.xsd#mmc_A3.875SeniorDebtObligationsDue2024Member"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_A3.875SeniorDebtObligationsDue2024Member_6e93c029-a5a8-41be-84e4-00625f51ce11" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A3.50SeniorDebtObligationsDue2025Member_f6e456ba-1443-4e37-b568-a09674e356a9" xlink:href="mmc-20210331.xsd#mmc_A3.50SeniorDebtObligationsDue2025Member"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_A3.50SeniorDebtObligationsDue2025Member_f6e456ba-1443-4e37-b568-a09674e356a9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A1.349SeniorDebtObligationsDue2026Member_1f7451f9-8508-484f-9ece-909626880bb3" xlink:href="mmc-20210331.xsd#mmc_A1.349SeniorDebtObligationsDue2026Member"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_A1.349SeniorDebtObligationsDue2026Member_1f7451f9-8508-484f-9ece-909626880bb3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A3.75SeniorDebtObligationsDue2026Member_0881b271-ffa3-4d6c-9c8f-b8b03246e572" xlink:href="mmc-20210331.xsd#mmc_A3.75SeniorDebtObligationsDue2026Member"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_A3.75SeniorDebtObligationsDue2026Member_0881b271-ffa3-4d6c-9c8f-b8b03246e572" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_SeniorDebtObligationsDue2029Member_080f1106-c1a3-4f19-8466-a7534835aa63" xlink:href="mmc-20210331.xsd#mmc_SeniorDebtObligationsDue2029Member"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_SeniorDebtObligationsDue2029Member_080f1106-c1a3-4f19-8466-a7534835aa63" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A1.979SeniorDebtObligationsDue2030Member_22ccfaa3-b034-4b7a-9629-2ba56d3aaadd" xlink:href="mmc-20210331.xsd#mmc_A1.979SeniorDebtObligationsDue2030Member"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_A1.979SeniorDebtObligationsDue2030Member_22ccfaa3-b034-4b7a-9629-2ba56d3aaadd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A2.250SeniorDebtObligationsDue2030Member_a12457a6-069a-4c80-9986-41d672ec0f19" xlink:href="mmc-20210331.xsd#mmc_A2.250SeniorDebtObligationsDue2030Member"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_A2.250SeniorDebtObligationsDue2030Member_a12457a6-069a-4c80-9986-41d672ec0f19" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_SeniorDebtObligationsDue2033Member_0c7a19e2-7020-4f38-8b98-6172b2ad1bcb" xlink:href="mmc-20210331.xsd#mmc_SeniorDebtObligationsDue2033Member"/>
    <link:presentationArc order="13" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_SeniorDebtObligationsDue2033Member_0c7a19e2-7020-4f38-8b98-6172b2ad1bcb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A4.75SeniorDebtObligationsDue2039Member_a57bfd00-297a-48ad-9477-88a5ea14d9dc" xlink:href="mmc-20210331.xsd#mmc_A4.75SeniorDebtObligationsDue2039Member"/>
    <link:presentationArc order="14" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_A4.75SeniorDebtObligationsDue2039Member_a57bfd00-297a-48ad-9477-88a5ea14d9dc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_SeniorDebtObligationDue2047Member_7938ea59-9609-4827-a20b-14c736e0d083" xlink:href="mmc-20210331.xsd#mmc_SeniorDebtObligationDue2047Member"/>
    <link:presentationArc order="15" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_SeniorDebtObligationDue2047Member_7938ea59-9609-4827-a20b-14c736e0d083" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_SeniorDebtObligationsDue2048Member_d371f08a-ca0f-4afe-9349-fcf57bd19037" xlink:href="mmc-20210331.xsd#mmc_SeniorDebtObligationsDue2048Member"/>
    <link:presentationArc order="16" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_SeniorDebtObligationsDue2048Member_d371f08a-ca0f-4afe-9349-fcf57bd19037" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A4.90SeniorDebtObligationsDue2049Member_a5da2a9f-b1d6-46f7-8304-624e33746ec3" xlink:href="mmc-20210331.xsd#mmc_A4.90SeniorDebtObligationsDue2049Member"/>
    <link:presentationArc order="17" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_A4.90SeniorDebtObligationsDue2049Member_a5da2a9f-b1d6-46f7-8304-624e33746ec3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_MortgageDue2035Member_1c8ba444-f72b-42d4-8a37-029a7ba239ad" xlink:href="mmc-20210331.xsd#mmc_MortgageDue2035Member"/>
    <link:presentationArc order="18" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_MortgageDue2035Member_1c8ba444-f72b-42d4-8a37-029a7ba239ad" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherDebtInstrumentsMember_b6a1e9b6-0cc4-4303-b6b5-278fa84ced45" xlink:href="mmc-20210331.xsd#mmc_OtherDebtInstrumentsMember"/>
    <link:presentationArc order="19" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_0a4d0a13-92e6-4178-9c65-505bf505fd46" xlink:to="loc_mmc_OtherDebtInstrumentsMember_b6a1e9b6-0cc4-4303-b6b5-278fa84ced45" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_96ec32ea-573f-4d37-96e9-37260d2b5c5b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentTable_0f5f8e28-6e69-4ad4-9ae4-f5271229acf9" xlink:to="loc_us-gaap_DebtInstrumentLineItems_96ec32ea-573f-4d37-96e9-37260d2b5c5b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_74084a28-3c35-4039-aed2-aa7ef855c488" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_96ec32ea-573f-4d37-96e9-37260d2b5c5b" xlink:to="loc_us-gaap_LongTermDebtCurrent_74084a28-3c35-4039-aed2-aa7ef855c488" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_b215b392-44ed-42a7-a386-87f8f4a5bc94" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtCurrent"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_96ec32ea-573f-4d37-96e9-37260d2b5c5b" xlink:to="loc_us-gaap_DebtCurrent_b215b392-44ed-42a7-a386-87f8f4a5bc94" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_3a654ad5-ff04-4512-b5d5-f6a5bc29f9b3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_96ec32ea-573f-4d37-96e9-37260d2b5c5b" xlink:to="loc_us-gaap_LongTermDebt_3a654ad5-ff04-4512-b5d5-f6a5bc29f9b3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_e7a8bb4b-6949-497b-934f-2c8241f9181c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_96ec32ea-573f-4d37-96e9-37260d2b5c5b" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_e7a8bb4b-6949-497b-934f-2c8241f9181c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_dd640b73-833d-45b5-b8d9-4aab6469567a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_96ec32ea-573f-4d37-96e9-37260d2b5c5b" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_dd640b73-833d-45b5-b8d9-4aab6469567a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/DebtNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#DebtNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/DebtNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtDisclosureAbstract_25e68765-cbc7-47fc-9a6e-6a9b7ce6e989" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_192d30cb-45ca-4a42-b2e9-7388ce18ea40" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtDisclosureAbstract_25e68765-cbc7-47fc-9a6e-6a9b7ce6e989" xlink:to="loc_us-gaap_DebtInstrumentTable_192d30cb-45ca-4a42-b2e9-7388ce18ea40" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_916c66dc-eb72-496f-ad51-dd1650a9c6d4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentTable_192d30cb-45ca-4a42-b2e9-7388ce18ea40" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_916c66dc-eb72-496f-ad51-dd1650a9c6d4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_dc6cf307-a7d8-4c59-b8a6-9c3e0192a287" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_916c66dc-eb72-496f-ad51-dd1650a9c6d4" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_dc6cf307-a7d8-4c59-b8a6-9c3e0192a287" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_7fd7e74d-d7e7-459b-a21b-18065dc7c062" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SeniorNotesMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_dc6cf307-a7d8-4c59-b8a6-9c3e0192a287" xlink:to="loc_us-gaap_SeniorNotesMember_7fd7e74d-d7e7-459b-a21b-18065dc7c062" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_FloatingRateNotesMember_cda42311-ee67-4377-b9a4-bb1ce68bc2c0" xlink:href="mmc-20210331.xsd#mmc_FloatingRateNotesMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_dc6cf307-a7d8-4c59-b8a6-9c3e0192a287" xlink:to="loc_mmc_FloatingRateNotesMember_cda42311-ee67-4377-b9a4-bb1ce68bc2c0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_17758b33-1b56-4aff-9805-5aeeab2f8f51" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentTable_192d30cb-45ca-4a42-b2e9-7388ce18ea40" xlink:to="loc_us-gaap_CreditFacilityAxis_17758b33-1b56-4aff-9805-5aeeab2f8f51" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_8bb21b6e-71fa-4271-832c-5677e74ca3d5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CreditFacilityAxis_17758b33-1b56-4aff-9805-5aeeab2f8f51" xlink:to="loc_us-gaap_CreditFacilityDomain_8bb21b6e-71fa-4271-832c-5677e74ca3d5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_ee78df5e-d945-4440-ae09-3ed3b1459983" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CreditFacilityDomain_8bb21b6e-71fa-4271-832c-5677e74ca3d5" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_ee78df5e-d945-4440-ae09-3ed3b1459983" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_TermLoanFacilityMember_9b0f8bb5-364f-44c4-aea6-49a8c6d5d45a" xlink:href="mmc-20210331.xsd#mmc_TermLoanFacilityMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CreditFacilityDomain_8bb21b6e-71fa-4271-832c-5677e74ca3d5" xlink:to="loc_mmc_TermLoanFacilityMember_9b0f8bb5-364f-44c4-aea6-49a8c6d5d45a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_1a9db12c-6178-4f6e-9e2a-dc166a6f99cd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentTable_192d30cb-45ca-4a42-b2e9-7388ce18ea40" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_1a9db12c-6178-4f6e-9e2a-dc166a6f99cd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_ea64ad4c-cd4f-4197-b9b7-86ee448ab4de" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_1a9db12c-6178-4f6e-9e2a-dc166a6f99cd" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_ea64ad4c-cd4f-4197-b9b7-86ee448ab4de" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_c1778bf7-3a1d-4b3d-bec0-170cef56ecfb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommercialPaperMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_ea64ad4c-cd4f-4197-b9b7-86ee448ab4de" xlink:to="loc_us-gaap_CommercialPaperMember_c1778bf7-3a1d-4b3d-bec0-170cef56ecfb" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_db91fdc1-5b6b-4413-9cdc-63b4f362a75c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentTable_192d30cb-45ca-4a42-b2e9-7388ce18ea40" xlink:to="loc_us-gaap_DebtInstrumentAxis_db91fdc1-5b6b-4413-9cdc-63b4f362a75c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_04722610-35f3-4974-a944-32ec53728624" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentAxis_db91fdc1-5b6b-4413-9cdc-63b4f362a75c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_04722610-35f3-4974-a944-32ec53728624" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_NewFacilityMember_f6bb1c56-60ad-432b-b27f-dbc3f6859b74" xlink:href="mmc-20210331.xsd#mmc_NewFacilityMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_04722610-35f3-4974-a944-32ec53728624" xlink:to="loc_mmc_NewFacilityMember_f6bb1c56-60ad-432b-b27f-dbc3f6859b74" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_AmendedRevolvingCreditFacilityAnd364DayFacilityMember_96f80efb-0d6b-4bb6-850b-64045bb8db0b" xlink:href="mmc-20210331.xsd#mmc_AmendedRevolvingCreditFacilityAnd364DayFacilityMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_04722610-35f3-4974-a944-32ec53728624" xlink:to="loc_mmc_AmendedRevolvingCreditFacilityAnd364DayFacilityMember_96f80efb-0d6b-4bb6-850b-64045bb8db0b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_AmendedRevolvingCreditFacilityMember_d03d301a-c2f2-4bda-863d-fc2d536aed27" xlink:href="mmc-20210331.xsd#mmc_AmendedRevolvingCreditFacilityMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_AmendedRevolvingCreditFacilityAnd364DayFacilityMember_96f80efb-0d6b-4bb6-850b-64045bb8db0b" xlink:to="loc_mmc_AmendedRevolvingCreditFacilityMember_d03d301a-c2f2-4bda-863d-fc2d536aed27" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A364DayFacilityMember_4b00130f-7596-4443-8a91-c2a7b04842b0" xlink:href="mmc-20210331.xsd#mmc_A364DayFacilityMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_AmendedRevolvingCreditFacilityAnd364DayFacilityMember_96f80efb-0d6b-4bb6-850b-64045bb8db0b" xlink:to="loc_mmc_A364DayFacilityMember_4b00130f-7596-4443-8a91-c2a7b04842b0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A500MillionOneYearTermLoanand500MillionTwoYearTermLoanMember_be656593-011f-42bb-9178-adebf00dc76e" xlink:href="mmc-20210331.xsd#mmc_A500MillionOneYearTermLoanand500MillionTwoYearTermLoanMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_04722610-35f3-4974-a944-32ec53728624" xlink:to="loc_mmc_A500MillionOneYearTermLoanand500MillionTwoYearTermLoanMember_be656593-011f-42bb-9178-adebf00dc76e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A500MillionOneYearTermLoanFacilityMember_dff47c36-0a3c-43a4-b19d-aaf6748f2d7a" xlink:href="mmc-20210331.xsd#mmc_A500MillionOneYearTermLoanFacilityMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_A500MillionOneYearTermLoanand500MillionTwoYearTermLoanMember_be656593-011f-42bb-9178-adebf00dc76e" xlink:to="loc_mmc_A500MillionOneYearTermLoanFacilityMember_dff47c36-0a3c-43a4-b19d-aaf6748f2d7a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A500MillionTwoYearTermLoanFacilityMember_a63eaab6-e4d4-4ee2-be5f-05ce80f18e92" xlink:href="mmc-20210331.xsd#mmc_A500MillionTwoYearTermLoanFacilityMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_mmc_A500MillionOneYearTermLoanand500MillionTwoYearTermLoanMember_be656593-011f-42bb-9178-adebf00dc76e" xlink:to="loc_mmc_A500MillionTwoYearTermLoanFacilityMember_a63eaab6-e4d4-4ee2-be5f-05ce80f18e92" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OtherDebtFacilitiesMember_dac8fd97-8ede-4a44-bb2d-567b8e94896e" xlink:href="mmc-20210331.xsd#mmc_OtherDebtFacilitiesMember"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_04722610-35f3-4974-a944-32ec53728624" xlink:to="loc_mmc_OtherDebtFacilitiesMember_dac8fd97-8ede-4a44-bb2d-567b8e94896e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_A2.250SeniorDebtObligationsDue2030Member_11f13ce7-b7d3-482a-b314-ec7747593239" xlink:href="mmc-20210331.xsd#mmc_A2.250SeniorDebtObligationsDue2030Member"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_04722610-35f3-4974-a944-32ec53728624" xlink:to="loc_mmc_A2.250SeniorDebtObligationsDue2030Member_11f13ce7-b7d3-482a-b314-ec7747593239" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_c4ba4de5-36cc-4288-90d8-bcd05a17a305" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentTable_192d30cb-45ca-4a42-b2e9-7388ce18ea40" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_c4ba4de5-36cc-4288-90d8-bcd05a17a305" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3936e69f-bfe9-4a2f-90ce-06ccd290f44d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_c4ba4de5-36cc-4288-90d8-bcd05a17a305" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3936e69f-bfe9-4a2f-90ce-06ccd290f44d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_61804ddb-59f7-44a1-beed-df6d75972cc6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_3936e69f-bfe9-4a2f-90ce-06ccd290f44d" xlink:to="loc_us-gaap_SubsequentEventMember_61804ddb-59f7-44a1-beed-df6d75972cc6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentTable_192d30cb-45ca-4a42-b2e9-7388ce18ea40" xlink:to="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_4aa0fdef-ce0f-45f3-8ec5-a7c6dc27a955" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermBorrowings"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_ShortTermBorrowings_4aa0fdef-ce0f-45f3-8ec5-a7c6dc27a955" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaper_ee518951-8f35-43b0-8a72-54283beef95f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommercialPaper"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_CommercialPaper_ee518951-8f35-43b0-8a72-54283beef95f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_3cd6f2c0-4ee8-4ca4-a969-2f7cc0b4b514" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_3cd6f2c0-4ee8-4ca4-a969-2f7cc0b4b514" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_6f764646-8541-418a-a93a-e693c497b2fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_DebtInstrumentTerm_6f764646-8541-418a-a93a-e693c497b2fd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_a5775475-2b53-4d3c-8a0a-f1cc081782d5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCredit"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_LineOfCredit_a5775475-2b53-4d3c-8a0a-f1cc081782d5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_b10c8f9b-d66a-4243-a21f-8c1c92d21a67" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_b10c8f9b-d66a-4243-a21f-8c1c92d21a67" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_2c81162b-da7a-4678-b535-04a6276307b1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_2c81162b-da7a-4678-b535-04a6276307b1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfDebt_54729d29-2996-42cb-8b35-e34ca19d8091" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfDebt"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_RepaymentsOfDebt_54729d29-2996-42cb-8b35-e34ca19d8091" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_753aa809-b341-44f6-8367-8536370221d3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_753aa809-b341-44f6-8367-8536370221d3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_212b8695-0b3e-4571-a925-76431310d2ea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtInstrumentLineItems_c8e816d3-fa41-41c4-baff-a0ebdd152cc2" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_212b8695-0b3e-4571-a925-76431310d2ea" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/DebtEstimatedFairValueofSignificantFinancialInstrumentsDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#DebtEstimatedFairValueofSignificantFinancialInstrumentsDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/DebtEstimatedFairValueofSignificantFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtDisclosureAbstract_ba3433ba-9fe0-411b-9a08-092b34dbfa22" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_5d0a4d17-74c5-4f6f-b81c-f2712c2c1950" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_DebtDisclosureAbstract_ba3433ba-9fe0-411b-9a08-092b34dbfa22" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_5d0a4d17-74c5-4f6f-b81c-f2712c2c1950" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_7612e66a-93ef-416d-9ed6-8bcbd96eb8db" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_5d0a4d17-74c5-4f6f-b81c-f2712c2c1950" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_7612e66a-93ef-416d-9ed6-8bcbd96eb8db" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_78fcdbed-3f57-4863-b76d-33823b822b65" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_7612e66a-93ef-416d-9ed6-8bcbd96eb8db" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_78fcdbed-3f57-4863-b76d-33823b822b65" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_cbbe51f8-4522-451d-bd39-6f6cb664200b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_78fcdbed-3f57-4863-b76d-33823b822b65" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_cbbe51f8-4522-451d-bd39-6f6cb664200b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_8317101f-9c3f-4f69-9fe6-5d5ff9e6df0e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_cbbe51f8-4522-451d-bd39-6f6cb664200b" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_8317101f-9c3f-4f69-9fe6-5d5ff9e6df0e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_0fedfe65-cbab-492c-aea6-a33fd5b71dfc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_cbbe51f8-4522-451d-bd39-6f6cb664200b" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_0fedfe65-cbab-492c-aea6-a33fd5b71dfc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_17c97ba1-b931-45fc-af7d-f13c1b304b91" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_5d0a4d17-74c5-4f6f-b81c-f2712c2c1950" xlink:to="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_17c97ba1-b931-45fc-af7d-f13c1b304b91" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShorttermDebtFairValue_2d4bfff9-1df5-41b1-9d56-f4caf6d6f239" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShorttermDebtFairValue"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_17c97ba1-b931-45fc-af7d-f13c1b304b91" xlink:to="loc_us-gaap_ShorttermDebtFairValue_2d4bfff9-1df5-41b1-9d56-f4caf6d6f239" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_0535b80f-4836-427f-ad2b-a27419a7fa8c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_17c97ba1-b931-45fc-af7d-f13c1b304b91" xlink:to="loc_us-gaap_LongTermDebtFairValue_0535b80f-4836-427f-ad2b-a27419a7fa8c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RestructuringCosts" xlink:type="simple" xlink:href="mmc-20210331.xsd#RestructuringCosts"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RestructuringCosts" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_9506135e-9208-436b-8136-39b95333efc9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringAndRelatedActivitiesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedActivitiesDisclosureTextBlock_c5077128-0556-4f09-aff2-d9514fc091fd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringAndRelatedActivitiesDisclosureTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_9506135e-9208-436b-8136-39b95333efc9" xlink:to="loc_us-gaap_RestructuringAndRelatedActivitiesDisclosureTextBlock_c5077128-0556-4f09-aff2-d9514fc091fd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RestructuringCostsTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#RestructuringCostsTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RestructuringCostsTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_fbaec9db-b40d-46c2-b532-3d2c71a7aee0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringAndRelatedActivitiesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringReserveByTypeOfCostTextBlock_b8e3edd5-5b41-4314-8701-c8e87e05d3aa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfRestructuringReserveByTypeOfCostTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_fbaec9db-b40d-46c2-b532-3d2c71a7aee0" xlink:to="loc_us-gaap_ScheduleOfRestructuringReserveByTypeOfCostTextBlock_b8e3edd5-5b41-4314-8701-c8e87e05d3aa" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RestructuringCostsNarrativeDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RestructuringCostsNarrativeDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RestructuringCostsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_097f40ab-5133-4b74-8172-f3812568a2b1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringAndRelatedActivitiesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_52492bee-c0bb-458f-a2c5-65f1feb52c08" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_097f40ab-5133-4b74-8172-f3812568a2b1" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_52492bee-c0bb-458f-a2c5-65f1feb52c08" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_0f80a6a8-dbc2-4c10-bee1-d300d7a7ce19" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_52492bee-c0bb-458f-a2c5-65f1feb52c08" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_0f80a6a8-dbc2-4c10-bee1-d300d7a7ce19" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_81f5e0e8-ef77-4670-bd81-c6e0b292e3bd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_0f80a6a8-dbc2-4c10-bee1-d300d7a7ce19" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_81f5e0e8-ef77-4670-bd81-c6e0b292e3bd" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_JardineLloydThompsonGroupplcMember_e7b29f55-6793-4783-9670-1052ee257a00" xlink:href="mmc-20210331.xsd#mmc_JardineLloydThompsonGroupplcMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_81f5e0e8-ef77-4670-bd81-c6e0b292e3bd" xlink:to="loc_mmc_JardineLloydThompsonGroupplcMember_e7b29f55-6793-4783-9670-1052ee257a00" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_2338f85f-5adb-4574-9932-c2b5c6087ef6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_52492bee-c0bb-458f-a2c5-65f1feb52c08" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_2338f85f-5adb-4574-9932-c2b5c6087ef6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_d3646905-286c-4e9d-8966-30b6da931f6c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_2338f85f-5adb-4574-9932-c2b5c6087ef6" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_d3646905-286c-4e9d-8966-30b6da931f6c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_AcquisitionRelatedMember_f6368161-b64f-4026-a2da-8eda0344c62f" xlink:href="mmc-20210331.xsd#mmc_AcquisitionRelatedMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_d3646905-286c-4e9d-8966-30b6da931f6c" xlink:to="loc_mmc_AcquisitionRelatedMember_f6368161-b64f-4026-a2da-8eda0344c62f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_SeveranceandFutureRentMember_69a54766-e8ef-4b04-996b-e9955985d0c2" xlink:href="mmc-20210331.xsd#mmc_SeveranceandFutureRentMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_d3646905-286c-4e9d-8966-30b6da931f6c" xlink:to="loc_mmc_SeveranceandFutureRentMember_69a54766-e8ef-4b04-996b-e9955985d0c2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_3b86149b-7410-4748-9178-d71358956e96" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_52492bee-c0bb-458f-a2c5-65f1feb52c08" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_3b86149b-7410-4748-9178-d71358956e96" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_eed3910d-9eba-4191-b2fb-ea64aa0a18de" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_3b86149b-7410-4748-9178-d71358956e96" xlink:to="loc_us-gaap_SegmentDomain_eed3910d-9eba-4191-b2fb-ea64aa0a18de" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_RiskandInsuranceServicesSegmentMember_b445833e-ffe3-40a8-80c2-9d88b5b8a625" xlink:href="mmc-20210331.xsd#mmc_RiskandInsuranceServicesSegmentMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_eed3910d-9eba-4191-b2fb-ea64aa0a18de" xlink:to="loc_mmc_RiskandInsuranceServicesSegmentMember_b445833e-ffe3-40a8-80c2-9d88b5b8a625" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_ConsultingSegmentMember_c84747d2-5d36-4d4d-b10d-46de2232d7c7" xlink:href="mmc-20210331.xsd#mmc_ConsultingSegmentMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_eed3910d-9eba-4191-b2fb-ea64aa0a18de" xlink:to="loc_mmc_ConsultingSegmentMember_c84747d2-5d36-4d4d-b10d-46de2232d7c7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_a9e0583c-498e-4c08-ad38-6f480c41f240" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsAxis"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_52492bee-c0bb-458f-a2c5-65f1feb52c08" xlink:to="loc_srt_ConsolidationItemsAxis_a9e0583c-498e-4c08-ad38-6f480c41f240" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_d2ebff13-c48a-41e3-a1bf-7093516892a2" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsAxis_a9e0583c-498e-4c08-ad38-6f480c41f240" xlink:to="loc_srt_ConsolidationItemsDomain_d2ebff13-c48a-41e3-a1bf-7093516892a2" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_c9095b13-e9ca-4c0c-8d53-0c94e1deefd7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsDomain_d2ebff13-c48a-41e3-a1bf-7093516892a2" xlink:to="loc_us-gaap_CorporateNonSegmentMember_c9095b13-e9ca-4c0c-8d53-0c94e1deefd7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_b75923e3-6018-48e5-bfba-5a6ae5dbf024" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_52492bee-c0bb-458f-a2c5-65f1feb52c08" xlink:to="loc_us-gaap_RestructuringCostAndReserveLineItems_b75923e3-6018-48e5-bfba-5a6ae5dbf024" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedCostCostIncurredToDate1_cc974539-3a31-4361-9d57-d8c9ccab8846" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringAndRelatedCostCostIncurredToDate1"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_b75923e3-6018-48e5-bfba-5a6ae5dbf024" xlink:to="loc_us-gaap_RestructuringAndRelatedCostCostIncurredToDate1_cc974539-3a31-4361-9d57-d8c9ccab8846" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_92479077-466c-4b6a-bee9-938a8e692c19" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCharges"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_b75923e3-6018-48e5-bfba-5a6ae5dbf024" xlink:to="loc_us-gaap_RestructuringCharges_92479077-466c-4b6a-bee9-938a8e692c19" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/RestructuringCostsRestructuringActivitiesDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#RestructuringCostsRestructuringActivitiesDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/RestructuringCostsRestructuringActivitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_d9e648c9-658d-4bbe-ba01-8605f317368c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringAndRelatedActivitiesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_726b78e5-3764-44e8-944b-38fb78be062c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringAndRelatedActivitiesAbstract_d9e648c9-658d-4bbe-ba01-8605f317368c" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_726b78e5-3764-44e8-944b-38fb78be062c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_31bcffdc-b174-4d50-bc13-b5d928333f77" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_726b78e5-3764-44e8-944b-38fb78be062c" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_31bcffdc-b174-4d50-bc13-b5d928333f77" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b908d293-b544-4229-bdcb-1b5ae11f91c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_31bcffdc-b174-4d50-bc13-b5d928333f77" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b908d293-b544-4229-bdcb-1b5ae11f91c5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_JardineLloydThompsonGroupplcMember_533847c3-c8ba-4ce6-83fb-bcb77f3463ac" xlink:href="mmc-20210331.xsd#mmc_JardineLloydThompsonGroupplcMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b908d293-b544-4229-bdcb-1b5ae11f91c5" xlink:to="loc_mmc_JardineLloydThompsonGroupplcMember_533847c3-c8ba-4ce6-83fb-bcb77f3463ac" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_283cacee-e561-48f9-acaf-bcae26de62a7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_726b78e5-3764-44e8-944b-38fb78be062c" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_283cacee-e561-48f9-acaf-bcae26de62a7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_c89303d4-afb0-417a-9dac-e745d1ea7489" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_283cacee-e561-48f9-acaf-bcae26de62a7" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_c89303d4-afb0-417a-9dac-e745d1ea7489" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_b6e254fa-5e18-4a7a-8eaf-34ac6780d034" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_c89303d4-afb0-417a-9dac-e745d1ea7489" xlink:to="loc_us-gaap_EmployeeSeveranceMember_b6e254fa-5e18-4a7a-8eaf-34ac6780d034" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_RealEstateRelatedCostsMember_69341266-31fb-4205-9aee-ab2d0e876154" xlink:href="mmc-20210331.xsd#mmc_RealEstateRelatedCostsMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_c89303d4-afb0-417a-9dac-e745d1ea7489" xlink:to="loc_mmc_RealEstateRelatedCostsMember_69341266-31fb-4205-9aee-ab2d0e876154" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_InformationTechnologyMember_4a186e4c-9fc2-458a-9ee4-2f08a71d1850" xlink:href="mmc-20210331.xsd#mmc_InformationTechnologyMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_c89303d4-afb0-417a-9dac-e745d1ea7489" xlink:to="loc_mmc_InformationTechnologyMember_4a186e4c-9fc2-458a-9ee4-2f08a71d1850" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_LegalConsultingandOtherOutsideServicesMember_08707f80-b62d-4ffe-bad2-3e4adbf41183" xlink:href="mmc-20210331.xsd#mmc_LegalConsultingandOtherOutsideServicesMember"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_c89303d4-afb0-417a-9dac-e745d1ea7489" xlink:to="loc_mmc_LegalConsultingandOtherOutsideServicesMember_08707f80-b62d-4ffe-bad2-3e4adbf41183" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRestructuringMember_c713fbcb-b148-48f9-8a67-78aeb721dcf8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherRestructuringMember"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_c89303d4-afb0-417a-9dac-e745d1ea7489" xlink:to="loc_us-gaap_OtherRestructuringMember_c713fbcb-b148-48f9-8a67-78aeb721dcf8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_8cf1ad09-60f3-4097-bf30-f5afc7486b8a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_726b78e5-3764-44e8-944b-38fb78be062c" xlink:to="loc_us-gaap_RestructuringCostAndReserveLineItems_8cf1ad09-60f3-4097-bf30-f5afc7486b8a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveRollForward_0fb32450-f07a-43d1-8592-9f3d1c02e450" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringReserveRollForward"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_8cf1ad09-60f3-4097-bf30-f5afc7486b8a" xlink:to="loc_us-gaap_RestructuringReserveRollForward_0fb32450-f07a-43d1-8592-9f3d1c02e450" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_88927b02-602f-46d2-8402-d0b7cea6ac05" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringReserve"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringReserveRollForward_0fb32450-f07a-43d1-8592-9f3d1c02e450" xlink:to="loc_us-gaap_RestructuringReserve_88927b02-602f-46d2-8402-d0b7cea6ac05" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_688b0d02-01b3-42c7-85b1-e3d2e587e3c8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCharges"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringReserveRollForward_0fb32450-f07a-43d1-8592-9f3d1c02e450" xlink:to="loc_us-gaap_RestructuringCharges_688b0d02-01b3-42c7-85b1-e3d2e587e3c8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRestructuring_3bd9d29c-7946-4516-8739-ea07f8803c90" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForRestructuring"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringReserveRollForward_0fb32450-f07a-43d1-8592-9f3d1c02e450" xlink:to="loc_us-gaap_PaymentsForRestructuring_3bd9d29c-7946-4516-8739-ea07f8803c90" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveSettledWithoutCash2_1bc5a830-8211-46f3-97a8-b14343745d6e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringReserveSettledWithoutCash2"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringReserveRollForward_0fb32450-f07a-43d1-8592-9f3d1c02e450" xlink:to="loc_us-gaap_RestructuringReserveSettledWithoutCash2_1bc5a830-8211-46f3-97a8-b14343745d6e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2009/role/negatedTerseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveTranslationAdjustment_50ce6d16-f2ee-47e8-ae61-d8e0f4c0be9a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringReserveTranslationAdjustment"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringReserveRollForward_0fb32450-f07a-43d1-8592-9f3d1c02e450" xlink:to="loc_us-gaap_RestructuringReserveTranslationAdjustment_50ce6d16-f2ee-47e8-ae61-d8e0f4c0be9a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_b7536948-1282-490b-900a-b7f0d3bc3678" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringReserve"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_RestructuringReserveRollForward_0fb32450-f07a-43d1-8592-9f3d1c02e450" xlink:to="loc_us-gaap_RestructuringReserve_b7536948-1282-490b-900a-b7f0d3bc3678" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/CommonStock" xlink:type="simple" xlink:href="mmc-20210331.xsd#CommonStock"/>
  <link:presentationLink xlink:role="http://mmc.com/role/CommonStock" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_21fa4de0-4d70-4fd7-82fa-331bb4249877" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityNoteDisclosureTextBlock_087707c8-71ed-4d7b-a84d-7ea6807f342e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityNoteDisclosureTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_21fa4de0-4d70-4fd7-82fa-331bb4249877" xlink:to="loc_us-gaap_StockholdersEquityNoteDisclosureTextBlock_087707c8-71ed-4d7b-a84d-7ea6807f342e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/CommonStockDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#CommonStockDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/CommonStockDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_3d264b7d-57ad-44a1-931c-dfa49ec077b5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfTreasuryStockTable_335cd031-bdfb-4358-b812-741937341588" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfTreasuryStockTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityAbstract_3d264b7d-57ad-44a1-931c-dfa49ec077b5" xlink:to="loc_us-gaap_ClassOfTreasuryStockTable_335cd031-bdfb-4358-b812-741937341588" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_3485786f-527d-4d74-83c8-18a7b1e39164" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_335cd031-bdfb-4358-b812-741937341588" xlink:to="loc_us-gaap_StatementClassOfStockAxis_3485786f-527d-4d74-83c8-18a7b1e39164" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_660fe8e8-8caf-4e59-8443-186cdc04ed1e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3485786f-527d-4d74-83c8-18a7b1e39164" xlink:to="loc_us-gaap_ClassOfStockDomain_660fe8e8-8caf-4e59-8443-186cdc04ed1e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_60f7cf28-ad6c-4e15-b0a9-08f75245ea3d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ClassOfStockDomain_660fe8e8-8caf-4e59-8443-186cdc04ed1e" xlink:to="loc_us-gaap_CommonStockMember_60f7cf28-ad6c-4e15-b0a9-08f75245ea3d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityClassOfTreasuryStockLineItems_5f914844-636b-4182-bc1b-2abbe4e1ffc3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityClassOfTreasuryStockLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_335cd031-bdfb-4358-b812-741937341588" xlink:to="loc_us-gaap_EquityClassOfTreasuryStockLineItems_5f914844-636b-4182-bc1b-2abbe4e1ffc3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_834fed03-54bc-4dfa-89f3-7cbf8b0fe6ea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_5f914844-636b-4182-bc1b-2abbe4e1ffc3" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_834fed03-54bc-4dfa-89f3-7cbf8b0fe6ea" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfEquity_ea5c4890-a654-4a7d-b633-d0272c18806e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForRepurchaseOfEquity"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_5f914844-636b-4182-bc1b-2abbe4e1ffc3" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfEquity_ea5c4890-a654-4a7d-b633-d0272c18806e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_aa0c3239-2664-4199-b87a-66ca30a75365" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_5f914844-636b-4182-bc1b-2abbe4e1ffc3" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_aa0c3239-2664-4199-b87a-66ca30a75365" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_b54dc9aa-bbed-4a31-8c93-f5589c321992" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_5f914844-636b-4182-bc1b-2abbe4e1ffc3" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_b54dc9aa-bbed-4a31-8c93-f5589c321992" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_6dce4996-ed8b-4613-abc0-54ef258e82c9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_5f914844-636b-4182-bc1b-2abbe4e1ffc3" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_6dce4996-ed8b-4613-abc0-54ef258e82c9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_bdd0154c-5b0f-4540-9329-a5b7b6cbdf5e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_5f914844-636b-4182-bc1b-2abbe4e1ffc3" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_bdd0154c-5b0f-4540-9329-a5b7b6cbdf5e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/ClaimsLawsuitsAndOtherContingencies" xlink:type="simple" xlink:href="mmc-20210331.xsd#ClaimsLawsuitsAndOtherContingencies"/>
  <link:presentationLink xlink:role="http://mmc.com/role/ClaimsLawsuitsAndOtherContingencies" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingenciesDisclosureAbstract_6ade5567-32c6-4a56-8c88-0925f8b6d6f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_c95c211d-3191-4cee-9b3a-281111be4465" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CommitmentsAndContingenciesDisclosureAbstract_6ade5567-32c6-4a56-8c88-0925f8b6d6f5" xlink:to="loc_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_c95c211d-3191-4cee-9b3a-281111be4465" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/ClaimsLawsuitsAndOtherContingenciesDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#ClaimsLawsuitsAndOtherContingenciesDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/ClaimsLawsuitsAndOtherContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingenciesDisclosureAbstract_db649ea2-86c0-42e3-8cd8-64908629b4d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_3c1bfb55-eb3f-4eb0-b601-5adf833c906b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingenciesTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_CommitmentsAndContingenciesDisclosureAbstract_db649ea2-86c0-42e3-8cd8-64908629b4d7" xlink:to="loc_us-gaap_LossContingenciesTable_3c1bfb55-eb3f-4eb0-b601-5adf833c906b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_bb47ecd1-27e1-4a10-9212-d7674ccc42ae" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_LegalEntityAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LossContingenciesTable_3c1bfb55-eb3f-4eb0-b601-5adf833c906b" xlink:to="loc_dei_LegalEntityAxis_bb47ecd1-27e1-4a10-9212-d7674ccc42ae" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_5d9cea86-79bc-4ed6-bff6-fbc6d88d987a" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_LegalEntityAxis_bb47ecd1-27e1-4a10-9212-d7674ccc42ae" xlink:to="loc_dei_EntityDomain_5d9cea86-79bc-4ed6-bff6-fbc6d88d987a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_JardineLloydThompsonGroupplcMember_02707c3a-c0a6-48bf-b573-03fc59aca683" xlink:href="mmc-20210331.xsd#mmc_JardineLloydThompsonGroupplcMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_EntityDomain_5d9cea86-79bc-4ed6-bff6-fbc6d88d987a" xlink:to="loc_mmc_JardineLloydThompsonGroupplcMember_02707c3a-c0a6-48bf-b573-03fc59aca683" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_6964b601-ee1c-4e92-95b0-245a7a2a9cb1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LossContingenciesTable_3c1bfb55-eb3f-4eb0-b601-5adf833c906b" xlink:to="loc_us-gaap_LossContingenciesLineItems_6964b601-ee1c-4e92-95b0-245a7a2a9cb1" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_IndividualCasesAnalyzed_566dfa48-10fd-4ec5-b32b-42ff6f08196f" xlink:href="mmc-20210331.xsd#mmc_IndividualCasesAnalyzed"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LossContingenciesLineItems_6964b601-ee1c-4e92-95b0-245a7a2a9cb1" xlink:to="loc_mmc_IndividualCasesAnalyzed_566dfa48-10fd-4ec5-b32b-42ff6f08196f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_c4f34651-915b-4e0d-8196-34e9ea3b5fdc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_LossContingenciesLineItems_6964b601-ee1c-4e92-95b0-245a7a2a9cb1" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_c4f34651-915b-4e0d-8196-34e9ea3b5fdc" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/SegmentInformation" xlink:type="simple" xlink:href="mmc-20210331.xsd#SegmentInformation"/>
  <link:presentationLink xlink:role="http://mmc.com/role/SegmentInformation" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingAbstract_ab6af33a-7921-45c4-b6aa-aa7aa0c20644" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingDisclosureTextBlock_5e9fce89-1be6-44ff-b571-2d0d57cb56b3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingDisclosureTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingAbstract_ab6af33a-7921-45c4-b6aa-aa7aa0c20644" xlink:to="loc_us-gaap_SegmentReportingDisclosureTextBlock_5e9fce89-1be6-44ff-b571-2d0d57cb56b3" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/SegmentInformationTables" xlink:type="simple" xlink:href="mmc-20210331.xsd#SegmentInformationTables"/>
  <link:presentationLink xlink:role="http://mmc.com/role/SegmentInformationTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingAbstract_c774d491-899c-49ca-94db-ff14e2918c3f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock_916226c1-b847-40a6-8d99-5443e9b97bf4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingAbstract_c774d491-899c-49ca-94db-ff14e2918c3f" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock_916226c1-b847-40a6-8d99-5443e9b97bf4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReconciliationOfRevenueFromSegmentsToConsolidatedTextBlock_a56477db-6c26-4ca4-b6f8-e3b3add8a25e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReconciliationOfRevenueFromSegmentsToConsolidatedTextBlock"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingAbstract_c774d491-899c-49ca-94db-ff14e2918c3f" xlink:to="loc_us-gaap_ReconciliationOfRevenueFromSegmentsToConsolidatedTextBlock_a56477db-6c26-4ca4-b6f8-e3b3add8a25e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/SegmentInformationSelectedInformationAndDetailsForMMCsOperatingSegmentsDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#SegmentInformationSelectedInformationAndDetailsForMMCsOperatingSegmentsDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/SegmentInformationSelectedInformationAndDetailsForMMCsOperatingSegmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingAbstract_32561437-9374-486b-a356-a757c90e8902" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_60168b67-4fa9-4887-a2e3-1af0edfae201" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingAbstract_32561437-9374-486b-a356-a757c90e8902" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_60168b67-4fa9-4887-a2e3-1af0edfae201" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_17bd7966-7909-46f8-9b3c-0c1996183d8b" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_60168b67-4fa9-4887-a2e3-1af0edfae201" xlink:to="loc_srt_ConsolidationItemsAxis_17bd7966-7909-46f8-9b3c-0c1996183d8b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_fcf9774a-2b31-4cb0-bde8-112d54c64a43" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsAxis_17bd7966-7909-46f8-9b3c-0c1996183d8b" xlink:to="loc_srt_ConsolidationItemsDomain_fcf9774a-2b31-4cb0-bde8-112d54c64a43" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_295ccad9-4be3-495e-a812-5bdf82efbbd6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsDomain_fcf9774a-2b31-4cb0-bde8-112d54c64a43" xlink:to="loc_us-gaap_OperatingSegmentsMember_295ccad9-4be3-495e-a812-5bdf82efbbd6" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_CorporateAndEliminationsMember_3198bf7d-b819-4508-b4c5-93adc6c68ff4" xlink:href="mmc-20210331.xsd#mmc_CorporateAndEliminationsMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsDomain_fcf9774a-2b31-4cb0-bde8-112d54c64a43" xlink:to="loc_mmc_CorporateAndEliminationsMember_3198bf7d-b819-4508-b4c5-93adc6c68ff4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_7cc57463-1f00-42dd-9d6c-35c9ec3f9bf9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsDomain_fcf9774a-2b31-4cb0-bde8-112d54c64a43" xlink:to="loc_us-gaap_IntersegmentEliminationMember_7cc57463-1f00-42dd-9d6c-35c9ec3f9bf9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_b6dc9362-94d8-40b1-8868-69376119cfb9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_60168b67-4fa9-4887-a2e3-1af0edfae201" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_b6dc9362-94d8-40b1-8868-69376119cfb9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_6efa9e8d-0fbd-4683-b9ec-35db4c050a05" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_b6dc9362-94d8-40b1-8868-69376119cfb9" xlink:to="loc_us-gaap_SegmentDomain_6efa9e8d-0fbd-4683-b9ec-35db4c050a05" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_RiskandInsuranceServicesSegmentMember_66bae440-b718-4186-8425-b780e29ce3e0" xlink:href="mmc-20210331.xsd#mmc_RiskandInsuranceServicesSegmentMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_6efa9e8d-0fbd-4683-b9ec-35db4c050a05" xlink:to="loc_mmc_RiskandInsuranceServicesSegmentMember_66bae440-b718-4186-8425-b780e29ce3e0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_ConsultingSegmentMember_eec7281c-a630-4ea3-87ff-9fb982b1b767" xlink:href="mmc-20210331.xsd#mmc_ConsultingSegmentMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_6efa9e8d-0fbd-4683-b9ec-35db4c050a05" xlink:to="loc_mmc_ConsultingSegmentMember_eec7281c-a630-4ea3-87ff-9fb982b1b767" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_0db0584c-6f3c-4b93-afb9-c55382fb064a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_60168b67-4fa9-4887-a2e3-1af0edfae201" xlink:to="loc_us-gaap_SegmentReportingInformationLineItems_0db0584c-6f3c-4b93-afb9-c55382fb064a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_33d7b282-ca2b-4db1-9118-058e0ce0a2f4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0db0584c-6f3c-4b93-afb9-c55382fb064a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_33d7b282-ca2b-4db1-9118-058e0ce0a2f4" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_7dd639cb-de2e-4433-a9ff-eae60d3da09b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0db0584c-6f3c-4b93-afb9-c55382fb064a" xlink:to="loc_us-gaap_OperatingIncomeLoss_7dd639cb-de2e-4433-a9ff-eae60d3da09b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_InterestIncomeFiduciaryAssets_ac77738e-6a31-4392-bb56-8634d60d2508" xlink:href="mmc-20210331.xsd#mmc_InterestIncomeFiduciaryAssets"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0db0584c-6f3c-4b93-afb9-c55382fb064a" xlink:to="loc_mmc_InterestIncomeFiduciaryAssets_ac77738e-6a31-4392-bb56-8634d60d2508" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/SegmentInformationDetailsofOperatingSegmentRevenueDetails" xlink:type="simple" xlink:href="mmc-20210331.xsd#SegmentInformationDetailsofOperatingSegmentRevenueDetails"/>
  <link:presentationLink xlink:role="http://mmc.com/role/SegmentInformationDetailsofOperatingSegmentRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingAbstract_d84ea6d7-1a6b-492d-abaa-3b7157f6f0b3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e5c2927b-9c38-4960-8a23-982ad475b93b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingAbstract_d84ea6d7-1a6b-492d-abaa-3b7157f6f0b3" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e5c2927b-9c38-4960-8a23-982ad475b93b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_86ad4136-0da8-4504-af98-65b9f8b1d919" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsAxis"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e5c2927b-9c38-4960-8a23-982ad475b93b" xlink:to="loc_srt_ConsolidationItemsAxis_86ad4136-0da8-4504-af98-65b9f8b1d919" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_b96df87d-96a9-4f60-a6f3-5ac5620d81ca" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsAxis_86ad4136-0da8-4504-af98-65b9f8b1d919" xlink:to="loc_srt_ConsolidationItemsDomain_b96df87d-96a9-4f60-a6f3-5ac5620d81ca" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_e12856f3-ddb1-4edd-b218-8eb2b7ee148e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsDomain_b96df87d-96a9-4f60-a6f3-5ac5620d81ca" xlink:to="loc_us-gaap_OperatingSegmentsMember_e12856f3-ddb1-4edd-b218-8eb2b7ee148e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_CorporateAndEliminationsMember_85e22027-5a42-450d-bc8b-a65ed9342e1c" xlink:href="mmc-20210331.xsd#mmc_CorporateAndEliminationsMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_srt_ConsolidationItemsDomain_b96df87d-96a9-4f60-a6f3-5ac5620d81ca" xlink:to="loc_mmc_CorporateAndEliminationsMember_85e22027-5a42-450d-bc8b-a65ed9342e1c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_060b829d-06a4-41f6-8ee2-48f51cce496a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e5c2927b-9c38-4960-8a23-982ad475b93b" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_060b829d-06a4-41f6-8ee2-48f51cce496a" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_70e7e51a-714c-4126-a451-c98e2d5c1e61" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_060b829d-06a4-41f6-8ee2-48f51cce496a" xlink:to="loc_us-gaap_SegmentDomain_70e7e51a-714c-4126-a451-c98e2d5c1e61" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_RiskandInsuranceServicesSegmentMember_51ca7f4e-7e38-4682-9b5e-32a4a34b2bf9" xlink:href="mmc-20210331.xsd#mmc_RiskandInsuranceServicesSegmentMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_70e7e51a-714c-4126-a451-c98e2d5c1e61" xlink:to="loc_mmc_RiskandInsuranceServicesSegmentMember_51ca7f4e-7e38-4682-9b5e-32a4a34b2bf9" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_ConsultingSegmentMember_489536c6-c5d9-42d6-8e2b-27014c3edaaf" xlink:href="mmc-20210331.xsd#mmc_ConsultingSegmentMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentDomain_70e7e51a-714c-4126-a451-c98e2d5c1e61" xlink:to="loc_mmc_ConsultingSegmentMember_489536c6-c5d9-42d6-8e2b-27014c3edaaf" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsAxis_916d3e9c-1e6d-4cdb-98c6-19245f2fc1c8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsegmentsAxis"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e5c2927b-9c38-4960-8a23-982ad475b93b" xlink:to="loc_us-gaap_SubsegmentsAxis_916d3e9c-1e6d-4cdb-98c6-19245f2fc1c8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsegmentsDomain_1a0b6b5c-c843-4d16-9ef0-3dfd66b03263" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsegmentsDomain"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsAxis_916d3e9c-1e6d-4cdb-98c6-19245f2fc1c8" xlink:to="loc_us-gaap_SubsegmentsDomain_1a0b6b5c-c843-4d16-9ef0-3dfd66b03263" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_MarshInsuranceGroupMember_fb051da8-2926-4ccf-a02f-78ec80d5976c" xlink:href="mmc-20210331.xsd#mmc_MarshInsuranceGroupMember"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_1a0b6b5c-c843-4d16-9ef0-3dfd66b03263" xlink:to="loc_mmc_MarshInsuranceGroupMember_fb051da8-2926-4ccf-a02f-78ec80d5976c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_GuyCarpenterReinsuranceGroupMember_73747bb2-7d0c-410b-9f62-b9210d3ecd16" xlink:href="mmc-20210331.xsd#mmc_GuyCarpenterReinsuranceGroupMember"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_1a0b6b5c-c843-4d16-9ef0-3dfd66b03263" xlink:to="loc_mmc_GuyCarpenterReinsuranceGroupMember_73747bb2-7d0c-410b-9f62-b9210d3ecd16" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_MercerConsultingGroupMember_91937926-09c0-40de-b33f-370e4dabc4f0" xlink:href="mmc-20210331.xsd#mmc_MercerConsultingGroupMember"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_1a0b6b5c-c843-4d16-9ef0-3dfd66b03263" xlink:to="loc_mmc_MercerConsultingGroupMember_91937926-09c0-40de-b33f-370e4dabc4f0" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_mmc_OliverWymanGroupConsultingGroupMember_21727ded-2197-4d9b-80e4-8dd680e772cf" xlink:href="mmc-20210331.xsd#mmc_OliverWymanGroupConsultingGroupMember"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SubsegmentsDomain_1a0b6b5c-c843-4d16-9ef0-3dfd66b03263" xlink:to="loc_mmc_OliverWymanGroupConsultingGroupMember_21727ded-2197-4d9b-80e4-8dd680e772cf" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_77b4e5e7-ab4c-449b-b6b0-9937f0323874" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e5c2927b-9c38-4960-8a23-982ad475b93b" xlink:to="loc_us-gaap_SegmentReportingInformationLineItems_77b4e5e7-ab4c-449b-b6b0-9937f0323874" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_5e854fab-4d45-409d-a0c3-290e5afba68d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_77b4e5e7-ab4c-449b-b6b0-9937f0323874" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_5e854fab-4d45-409d-a0c3-290e5afba68d" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
  <link:roleRef roleURI="http://mmc.com/role/NewAccountingGuidance" xlink:type="simple" xlink:href="mmc-20210331.xsd#NewAccountingGuidance"/>
  <link:presentationLink xlink:role="http://mmc.com/role/NewAccountingGuidance" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract_1c57faae-8559-4e7e-b3c1-237f03cdc344" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock_ef53baac-a632-43e5-865b-a0fa1020d2a7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesAbstract_1c57faae-8559-4e7e-b3c1-237f03cdc344" xlink:to="loc_us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock_ef53baac-a632-43e5-865b-a0fa1020d2a7" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
</link:linkbase>
