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  <xs:element id="mmc_UnitedStatesandCanadaMember" abstract="true" name="UnitedStatesandCanadaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_A4.75SeniorDebtObligationsDue2039Member" abstract="true" name="A4.75SeniorDebtObligationsDue2039Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure" abstract="false" name="BusinessCombinationContingentConsiderationLiabilityFairValueDisclosure" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_ProceedsFromContingentConsiderationPriorPeriodDispositions" abstract="false" name="ProceedsFromContingentConsiderationPriorPeriodDispositions" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_UnitedKingdomPensionandPostretirementBenefitPlanDefinedBenefitMember" abstract="true" name="UnitedKingdomPensionandPostretirementBenefitPlanDefinedBenefitMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_AccumulatedDefinedBenefitPlansAdjustmentForeignCurrencyTranslationAdjustmentsAttributableToParentMember" abstract="true" name="AccumulatedDefinedBenefitPlansAdjustmentForeignCurrencyTranslationAdjustmentsAttributableToParentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_RealEstateLeaseMember" abstract="true" name="RealEstateLeaseMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_A2375SeniorDebtObligationsDue2031Member" abstract="true" name="A2375SeniorDebtObligationsDue2031Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_StockIssuedDuringPeriodValueSharebasedCompensationandEmployeeStockPurchasePlanAndRelatedTaxDeficiency" abstract="false" name="StockIssuedDuringPeriodValueSharebasedCompensationandEmployeeStockPurchasePlanAndRelatedTaxDeficiency" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_FiduciaryLiabilitiesNetNoncurrent" abstract="false" name="FiduciaryLiabilitiesNetNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_LiabilityForErrorsAndOmissions" abstract="false" name="LiabilityForErrorsAndOmissions" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_PaymentsForPreviousAcquisitionDeferredConsideration" abstract="false" name="PaymentsForPreviousAcquisitionDeferredConsideration" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_AdvanceAssetManagementMember" abstract="true" name="AdvanceAssetManagementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_InformationTechnologyMember" abstract="true" name="InformationTechnologyMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_UncollectedPremiumsandClaimsNetofRelatedPayables" abstract="false" name="UncollectedPremiumsandClaimsNetofRelatedPayables" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_LesseeOperatingLeaseLeaseNotYetCommencedAmount" abstract="false" name="LesseeOperatingLeaseLeaseNotYetCommencedAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_LeasesRightOfUseAssetAmortization" abstract="false" name="LeasesRightOfUseAssetAmortization" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_A5750SeniorDebtObligationsDue2032Member" abstract="true" name="A5750SeniorDebtObligationsDue2032Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_SeniorDebtObligationsDue2048Member" abstract="true" name="SeniorDebtObligationsDue2048Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_FiduciaryAssetsFairValueDisclosure" abstract="false" name="FiduciaryAssetsFairValueDisclosure" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_InterestIncomeFiduciaryAssets" abstract="false" name="InterestIncomeFiduciaryAssets" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_CashandInvestmentsHeldinFiduciaryCapacityNoncurrent" abstract="false" name="CashandInvestmentsHeldinFiduciaryCapacityNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_SeveranceAndLeaseExitChargesMember" abstract="true" name="SeveranceAndLeaseExitChargesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_AdvancedPremiumsandClaimsReceivableGrossCurrent" abstract="false" name="AdvancedPremiumsandClaimsReceivableGrossCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_ReceiptsOfContingentConsiderationForDispositions" abstract="false" name="ReceiptsOfContingentConsiderationForDispositions" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_PaymentsToAcquireBusinessesNetOfCashAcquiredAndCashHeldInAFiduciaryCapacityAcquired" abstract="false" name="PaymentsToAcquireBusinessesNetOfCashAcquiredAndCashHeldInAFiduciaryCapacityAcquired" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_ProceedsFromContingentPurchaseConsiderationAsset" abstract="false" name="ProceedsFromContingentPurchaseConsiderationAsset" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_LegalConsultingandOtherOutsideServicesMember" abstract="true" name="LegalConsultingandOtherOutsideServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_FiniteLivedIntangibleAssetExpectedAmortizationafterYearFour" abstract="false" name="FiniteLivedIntangibleAssetExpectedAmortizationafterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_AccumulatedDefinedBenefitPlansAdjustmentOtherAdjustmentAttributableToParentMember" abstract="true" name="AccumulatedDefinedBenefitPlansAdjustmentOtherAdjustmentAttributableToParentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_PaymentsForAcquisitionsDeferredAndContingentConsideration" abstract="false" name="PaymentsForAcquisitionsDeferredAndContingentConsideration" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_SmallIndividualFinancialAdvisoryBusinessMember" abstract="true" name="SmallIndividualFinancialAdvisoryBusinessMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_A3.875SeniorDebtObligationsDue2024Member" abstract="true" name="A3.875SeniorDebtObligationsDue2024Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_RealEstateRelatedCostsMember" abstract="true" name="RealEstateRelatedCostsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_SeniorDebtObligationsDue2033Member" abstract="true" name="SeniorDebtObligationsDue2033Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_UncommittedCreditFacilityMember" abstract="true" name="UncommittedCreditFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_OtherReceivablesMember" abstract="true" name="OtherReceivablesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_A290SeniorDebtObligationsDue2051Member" abstract="true" name="A290SeniorDebtObligationsDue2051Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_FiduciaryAssetsAndLiabilitiesAbstract" abstract="true" name="FiduciaryAssetsAndLiabilitiesAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="mmc_HealthMember" abstract="true" name="HealthMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_CommitmentsForPotentialFutureInvestments" abstract="false" name="CommitmentsForPotentialFutureInvestments" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_RiskandInsuranceServicesSegmentMember" abstract="true" name="RiskandInsuranceServicesSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_FiduciaryAssetsAbstract" abstract="true" name="FiduciaryAssetsAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
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  <xs:element id="mmc_PaymentToAcquireBusinessesNetOfCashAndCashHeldInAFiduciaryCapacityAcquired" abstract="false" name="PaymentToAcquireBusinessesNetOfCashAndCashHeldInAFiduciaryCapacityAcquired" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_BusinessCombinationConsiderationTransferredAssetsAcquired" abstract="false" name="BusinessCombinationConsiderationTransferredAssetsAcquired" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_FiduciaryAssetsAndLiabilitiesTable" abstract="true" name="FiduciaryAssetsAndLiabilitiesTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="mmc_ProceedsFromPreviousDispositionContingentConsideration" abstract="false" name="ProceedsFromPreviousDispositionContingentConsideration" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_A3.50SeniorDebtObligationsDue2025Member" abstract="true" name="A3.50SeniorDebtObligationsDue2025Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_MarshInsuranceGroupMember" abstract="true" name="MarshInsuranceGroupMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_GainLossOnConsolidationOfBusiness" abstract="false" name="GainLossOnConsolidationOfBusiness" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_A3.75SeniorDebtObligationsDue2026Member" abstract="true" name="A3.75SeniorDebtObligationsDue2026Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_ConsultingSegmentMember" abstract="true" name="ConsultingSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_A1.979SeniorDebtObligationsDue2030Member" abstract="true" name="A1.979SeniorDebtObligationsDue2030Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_RevenueFromContractWithCustomerThresholdPercentageOfTotalRevenue" abstract="false" name="RevenueFromContractWithCustomerThresholdPercentageOfTotalRevenue" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="mmc_CareerMember" abstract="true" name="CareerMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense" abstract="false" name="PensionandOtherPostretirementBenefitContributionsInExcessofCurrentYearExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mmc_A330SeniorDebtObligationsDueMarch2023Member" abstract="true" name="A330SeniorDebtObligationsDueMarch2023Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mmc_SeniorDebtObligationsDue2024Member" abstract="true" name="SeniorDebtObligationsDue2024Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
