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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019c9a8b-96b8-72d6-b308-15025b1f9c3f,g:d2450e45-62cc-4e50-90b8-dfdf8180808e-->
<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" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.modernatx.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="mrna-20260331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c9a8b-980d-7352-940a-5d52e5ab8063" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_StatementTable_019c9a8b-980d-7352-940a-5d52e5ab8063" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7756-917d-6c9ef4600097" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c9a8b-980d-7352-940a-5d52e5ab8063" xlink:to="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7756-917d-6c9ef4600097" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7756-917d-6c9ef4600097_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7756-917d-6c9ef4600097" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7756-917d-6c9ef4600097_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7ac4-8d94-d8f460c6aa02" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7756-917d-6c9ef4600097" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7ac4-8d94-d8f460c6aa02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ProductSalesMember_019c9a8b-980d-7c01-9a8a-cf0c77670758" xlink:href="mrna-20260331.xsd#mrna_ProductSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7ac4-8d94-d8f460c6aa02" xlink:to="loc_mrna_ProductSalesMember_019c9a8b-980d-7c01-9a8a-cf0c77670758" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_019c9a8b-980d-70fc-8606-699287813530" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7ac4-8d94-d8f460c6aa02" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_019c9a8b-980d-70fc-8606-699287813530" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_019c9a8b-980d-7a6f-9cb8-fed37913056f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_RevenuesAbstract_019c9a8b-980d-7a6f-9cb8-fed37913056f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9a8b-980d-7d1e-8cbf-c964af94a7b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019c9a8b-980d-7a6f-9cb8-fed37913056f" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9a8b-980d-7d1e-8cbf-c964af94a7b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_019c9a8b-980d-783c-b0b4-f62f1a202ebb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_OperatingExpensesAbstract_019c9a8b-980d-783c-b0b4-f62f1a202ebb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019c9a8b-980d-740c-909a-a76235daee0f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019c9a8b-980d-783c-b0b4-f62f1a202ebb" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019c9a8b-980d-740c-909a-a76235daee0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019c9a8b-980d-736a-b32b-64a8f41b98f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019c9a8b-980d-783c-b0b4-f62f1a202ebb" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019c9a8b-980d-736a-b32b-64a8f41b98f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019c9a8b-980d-77e1-a5f5-7392028a2c9a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019c9a8b-980d-783c-b0b4-f62f1a202ebb" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019c9a8b-980d-77e1-a5f5-7392028a2c9a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019c9a8b-980d-7108-b2c7-4991a94fddef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019c9a8b-980d-783c-b0b4-f62f1a202ebb" xlink:to="loc_us-gaap_CostsAndExpenses_019c9a8b-980d-7108-b2c7-4991a94fddef" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019c9a8b-980d-7e55-be96-46e6eab79077" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_OperatingIncomeLoss_019c9a8b-980d-7e55-be96-46e6eab79077" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_019c9a8b-980d-7c79-9a7c-a4b503ebf807" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_InvestmentIncomeInterest_019c9a8b-980d-7c79-9a7c-a4b503ebf807" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019c9a8b-980d-7063-92a7-19c5ab88f69f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019c9a8b-980d-7063-92a7-19c5ab88f69f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c9a8b-980d-743f-a871-e571e8d2daa5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c9a8b-980d-743f-a871-e571e8d2daa5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019c9a8b-980d-7a72-909d-1649ecdf7a95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019c9a8b-980d-7a72-909d-1649ecdf7a95" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019c9a8b-980d-72be-afa1-c24706ae834d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_NetIncomeLoss_019c9a8b-980d-72be-afa1-c24706ae834d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_019c9a8b-980d-74d0-90e3-80119d5ddbd7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_EarningsPerShareAbstract_019c9a8b-980d-74d0-90e3-80119d5ddbd7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019c9a8b-980d-754f-a035-7facd2a5b35f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019c9a8b-980d-74d0-90e3-80119d5ddbd7" xlink:to="loc_us-gaap_EarningsPerShareBasic_019c9a8b-980d-754f-a035-7facd2a5b35f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019c9a8b-980d-73f9-9d0f-420370608a3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019c9a8b-980d-74d0-90e3-80119d5ddbd7" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019c9a8b-980d-73f9-9d0f-420370608a3f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_019c9a8b-980d-7758-b8fa-feaa716b7e58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-74e4-9cea-c4667c82e869" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_019c9a8b-980d-7758-b8fa-feaa716b7e58" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019c9a8b-980d-7aa3-8878-23b4e804203e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_019c9a8b-980d-7758-b8fa-feaa716b7e58" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019c9a8b-980d-7aa3-8878-23b4e804203e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019c9a8b-980d-72b2-aea2-12bbbc34b632" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_019c9a8b-980d-7758-b8fa-feaa716b7e58" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019c9a8b-980d-72b2-aea2-12bbbc34b632" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="simple" xlink:href="mrna-20260331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c9a8b-980d-7a2b-bc2c-1d6311cc2d88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c9a8b-980d-7175-9e5b-d24a8a6bd4c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-7a2b-bc2c-1d6311cc2d88" xlink:to="loc_us-gaap_StatementTable_019c9a8b-980d-7175-9e5b-d24a8a6bd4c0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c9a8b-980d-778b-a977-3c784cd77e28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c9a8b-980d-7175-9e5b-d24a8a6bd4c0" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c9a8b-980d-778b-a977-3c784cd77e28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-778b-a977-3c784cd77e28_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c9a8b-980d-778b-a977-3c784cd77e28" xlink:to="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-778b-a977-3c784cd77e28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-79c9-b451-9fe4197ab809" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c9a8b-980d-778b-a977-3c784cd77e28" xlink:to="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-79c9-b451-9fe4197ab809" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019c9a8b-980d-7a7d-a68b-041e64930427" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-79c9-b451-9fe4197ab809" xlink:to="loc_us-gaap_CommonStockMember_019c9a8b-980d-7a7d-a68b-041e64930427" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019c9a8b-980d-7805-a20f-2103823b1737" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-79c9-b451-9fe4197ab809" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019c9a8b-980d-7805-a20f-2103823b1737" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c9a8b-980d-706c-9ba7-ed763da1ec3e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-79c9-b451-9fe4197ab809" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c9a8b-980d-706c-9ba7-ed763da1ec3e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019c9a8b-980d-7dad-bf57-60312ca80d8c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-79c9-b451-9fe4197ab809" xlink:to="loc_us-gaap_RetainedEarningsMember_019c9a8b-980d-7dad-bf57-60312ca80d8c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9a8b-980d-7a2b-bc2c-1d6311cc2d88" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019c9a8b-980d-70c1-983d-46543dd8ab82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019c9a8b-980d-70c1-983d-46543dd8ab82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c9a8b-980d-72cc-aea4-e7f1e938e0c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:to="loc_us-gaap_StockholdersEquity_019c9a8b-980d-72cc-aea4-e7f1e938e0c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_019c9a8b-980d-7c90-b79d-a59b9e00bca9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_019c9a8b-980d-7c90-b79d-a59b9e00bca9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_019d9e35-8adf-7794-bf6b-a50644d8e053" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_019d9e35-8adf-7794-bf6b-a50644d8e053" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_019c9a8b-980d-7ff1-a67a-e40b6bd03a0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_019c9a8b-980d-7ff1-a67a-e40b6bd03a0c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019c9a8b-980d-7f4b-8907-15fa610de40d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_019c9a8b-980d-7f4b-8907-15fa610de40d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019c9a8b-980d-7680-aaf9-0d83dd69e7ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019c9a8b-980d-7680-aaf9-0d83dd69e7ff" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019c9a8b-980d-7248-81ef-4907dc95ae9e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019c9a8b-980d-7248-81ef-4907dc95ae9e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019c9a8b-980d-7121-b6ff-b9c0056c4555" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9a8b-980d-7974-bb7e-b717cb9c397c" xlink:to="loc_us-gaap_NetIncomeLoss_019c9a8b-980d-7121-b6ff-b9c0056c4555" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019c9a8b-980d-7b06-9d0b-52fec3d457e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c9a8b-980d-70a2-ae7c-46a02fdb5900" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/SummaryofBasisofPresentationandRecentAccountingStandardsScheduleofComponentsofAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#SummaryofBasisofPresentationandRecentAccountingStandardsScheduleofComponentsofAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/SummaryofBasisofPresentationandRecentAccountingStandardsScheduleofComponentsofAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c9a8b-980d-7aea-8b6f-35f1359e2e15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c9a8b-980d-7c3b-b2dd-87456f6a6c45" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c9a8b-980d-7aea-8b6f-35f1359e2e15" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c9a8b-980d-7c3b-b2dd-87456f6a6c45" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c9a8b-980d-7180-839a-bb5cd43de260" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019c9a8b-980d-7c3b-b2dd-87456f6a6c45" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c9a8b-980d-7180-839a-bb5cd43de260" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-7180-839a-bb5cd43de260_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c9a8b-980d-7180-839a-bb5cd43de260" xlink:to="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-7180-839a-bb5cd43de260_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-7780-8a4e-a0943b13d8dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c9a8b-980d-7180-839a-bb5cd43de260" xlink:to="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-7780-8a4e-a0943b13d8dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c9a8b-980d-7a3a-9026-e6b21fba7d13" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9a8b-980d-7780-8a4e-a0943b13d8dc" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c9a8b-980d-7a3a-9026-e6b21fba7d13" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019c9a8b-980d-7627-8e9d-0d457a9392fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c9a8b-980d-7a3a-9026-e6b21fba7d13" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_019c9a8b-980d-7627-8e9d-0d457a9392fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019c9a8b-980d-71ab-a1cc-5c0c579d1ec4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c9a8b-980d-7a3a-9026-e6b21fba7d13" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019c9a8b-980d-71ab-a1cc-5c0c579d1ec4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019c9a8b-980d-7e34-9975-d543423ed6ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c9a8b-980d-7a3a-9026-e6b21fba7d13" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019c9a8b-980d-7e34-9975-d543423ed6ae" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c9a8b-980d-795b-8869-c0f97de14405" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019c9a8b-980d-7aea-8b6f-35f1359e2e15" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c9a8b-980d-795b-8869-c0f97de14405" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c9a8b-980d-7c24-b29e-9fd6705717bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c9a8b-980d-795b-8869-c0f97de14405" xlink:to="loc_us-gaap_StockholdersEquity_019c9a8b-980d-7c24-b29e-9fd6705717bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019c9a8b-980d-7aeb-9618-19325cf611ab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_019c9a8b-980d-795b-8869-c0f97de14405" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019c9a8b-980d-7aeb-9618-19325cf611ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019c9a8b-980d-7fc0-83a8-ea516bfd51c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/NetProductSalesScheduleofRevenuefromExternalCustomersbyGeographicAreasDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#NetProductSalesScheduleofRevenuefromExternalCustomersbyGeographicAreasDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/NetProductSalesScheduleofRevenuefromExternalCustomersbyGeographicAreasDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-7cb1-8b3f-374d9f575360" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-70e5-a8b2-005e4a12cc3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-7cb1-8b3f-374d9f575360" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-70e5-a8b2-005e4a12cc3f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019c9a8b-980d-70b3-866c-6df7540d7d20" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-70e5-a8b2-005e4a12cc3f" xlink:to="loc_srt_StatementGeographicalAxis_019c9a8b-980d-70b3-866c-6df7540d7d20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019c9a8b-980d-70b3-866c-6df7540d7d20_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019c9a8b-980d-70b3-866c-6df7540d7d20" xlink:to="loc_srt_SegmentGeographicalDomain_019c9a8b-980d-70b3-866c-6df7540d7d20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019c9a8b-980d-73f1-b85b-8e8841c4791f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019c9a8b-980d-70b3-866c-6df7540d7d20" xlink:to="loc_srt_SegmentGeographicalDomain_019c9a8b-980d-73f1-b85b-8e8841c4791f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019c9a8b-980d-726d-b935-ab1fb5df3a60" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019c9a8b-980d-73f1-b85b-8e8841c4791f" xlink:to="loc_country_US_019c9a8b-980d-726d-b935-ab1fb5df3a60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EuropeMember_019c9a8b-980d-7535-abbf-df8aa0e77ba1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EuropeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019c9a8b-980d-73f1-b85b-8e8841c4791f" xlink:to="loc_srt_EuropeMember_019c9a8b-980d-7535-abbf-df8aa0e77ba1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_RestOfTheWorldMember_019c9a8b-980d-7234-afc4-5b7fb62406c1" xlink:href="mrna-20260331.xsd#mrna_RestOfTheWorldMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019c9a8b-980d-73f1-b85b-8e8841c4791f" xlink:to="loc_mrna_RestOfTheWorldMember_019c9a8b-980d-7234-afc4-5b7fb62406c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7bb2-9af7-f5d1a74327da" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-70e5-a8b2-005e4a12cc3f" xlink:to="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7bb2-9af7-f5d1a74327da" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7bb2-9af7-f5d1a74327da_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7bb2-9af7-f5d1a74327da" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7bb2-9af7-f5d1a74327da_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-71ad-abc1-446c733318ed" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7bb2-9af7-f5d1a74327da" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-71ad-abc1-446c733318ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ProductSalesMember_019c9a8b-980d-7b7d-9bd7-aeafe58ecece" xlink:href="mrna-20260331.xsd#mrna_ProductSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-71ad-abc1-446c733318ed" xlink:to="loc_mrna_ProductSalesMember_019c9a8b-980d-7b7d-9bd7-aeafe58ecece" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_COVID19Member_019c9a8b-980d-7181-96b4-567ad19fe385" xlink:href="mrna-20260331.xsd#mrna_COVID19Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ProductSalesMember_019c9a8b-980d-7b7d-9bd7-aeafe58ecece" xlink:to="loc_mrna_COVID19Member_019c9a8b-980d-7181-96b4-567ad19fe385" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_RSVMember_019c9a8b-980d-7b19-bc50-cbff4e857808" xlink:href="mrna-20260331.xsd#mrna_RSVMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ProductSalesMember_019c9a8b-980d-7b7d-9bd7-aeafe58ecece" xlink:to="loc_mrna_RSVMember_019c9a8b-980d-7b19-bc50-cbff4e857808" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9a8b-980d-70ac-8458-8e56c72f6819" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-7cb1-8b3f-374d9f575360" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9a8b-980d-70ac-8458-8e56c72f6819" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/NetProductSalesNarrativeDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#NetProductSalesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/NetProductSalesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-711a-8076-2c13e3189dc3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-7adc-a7dd-041d0b3d0c84" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-711a-8076-2c13e3189dc3" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-7adc-a7dd-041d0b3d0c84" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7231-87e8-5dd9a533ef35" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-7adc-a7dd-041d0b3d0c84" xlink:to="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7231-87e8-5dd9a533ef35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7231-87e8-5dd9a533ef35_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7231-87e8-5dd9a533ef35" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7231-87e8-5dd9a533ef35_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-76a4-b6a0-1e9601225f42" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7231-87e8-5dd9a533ef35" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-76a4-b6a0-1e9601225f42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ProductSalesMember_019c9a8b-980d-753c-a88a-99c92304f0ab" xlink:href="mrna-20260331.xsd#mrna_ProductSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-76a4-b6a0-1e9601225f42" xlink:to="loc_mrna_ProductSalesMember_019c9a8b-980d-753c-a88a-99c92304f0ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_NumberOfCommercialProducts_019c9a8b-980d-7482-ade4-81a7578b1267" xlink:href="mrna-20260331.xsd#mrna_NumberOfCommercialProducts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-711a-8076-2c13e3189dc3" xlink:to="loc_mrna_NumberOfCommercialProducts_019c9a8b-980d-7482-ade4-81a7578b1267" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/NetProductSalesScheduleofDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#NetProductSalesScheduleofDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/NetProductSalesScheduleofDisaggregationofRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-73ec-aa8f-e892ed6be8f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-7bc6-9b7c-81e9e129f039" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-73ec-aa8f-e892ed6be8f8" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-7bc6-9b7c-81e9e129f039" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7aa4-8898-057048e6a628" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-7bc6-9b7c-81e9e129f039" xlink:to="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7aa4-8898-057048e6a628" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7aa4-8898-057048e6a628_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7aa4-8898-057048e6a628" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7aa4-8898-057048e6a628_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-73f3-aba6-cef55009738f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7aa4-8898-057048e6a628" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-73f3-aba6-cef55009738f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ProductSalesMember_019c9a8b-980d-73e2-9342-d273c4cfd777" xlink:href="mrna-20260331.xsd#mrna_ProductSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-73f3-aba6-cef55009738f" xlink:to="loc_mrna_ProductSalesMember_019c9a8b-980d-73e2-9342-d273c4cfd777" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_RevenueFromContractWithCustomerExcludingAssessedTaxGross_019c9a8b-980d-7040-866b-b4d5b9b2681d" xlink:href="mrna-20260331.xsd#mrna_RevenueFromContractWithCustomerExcludingAssessedTaxGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-73ec-aa8f-e892ed6be8f8" xlink:to="loc_mrna_RevenueFromContractWithCustomerExcludingAssessedTaxGross_019c9a8b-980d-7040-866b-b4d5b9b2681d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ContractWithCustomerLiabilityProvisionForChargebacksDiscountsAndFees_019c9a8b-980d-7c48-abc9-f6a74e0857c6" xlink:href="mrna-20260331.xsd#mrna_ContractWithCustomerLiabilityProvisionForChargebacksDiscountsAndFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-73ec-aa8f-e892ed6be8f8" xlink:to="loc_mrna_ContractWithCustomerLiabilityProvisionForChargebacksDiscountsAndFees_019c9a8b-980d-7c48-abc9-f6a74e0857c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ContractWithCustomerLiabilityProvisionForRefundsRebatesAndOtherFees_019c9a8b-980d-7481-898e-d255e22ef411" xlink:href="mrna-20260331.xsd#mrna_ContractWithCustomerLiabilityProvisionForRefundsRebatesAndOtherFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-73ec-aa8f-e892ed6be8f8" xlink:to="loc_mrna_ContractWithCustomerLiabilityProvisionForRefundsRebatesAndOtherFees_019c9a8b-980d-7481-898e-d255e22ef411" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ContractWithCustomerLiabilityProvision_019c9a8b-980d-735d-8def-6670ff69e9c6" xlink:href="mrna-20260331.xsd#mrna_ContractWithCustomerLiabilityProvision"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-73ec-aa8f-e892ed6be8f8" xlink:to="loc_mrna_ContractWithCustomerLiabilityProvision_019c9a8b-980d-735d-8def-6670ff69e9c6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9a8b-980d-7e8f-8eed-f046fbab5e86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-73ec-aa8f-e892ed6be8f8" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9a8b-980d-7e8f-8eed-f046fbab5e86" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/NetProductSalesScheduleofChangesinBalancesofReceivablesandContractLiabilitiesDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#NetProductSalesScheduleofChangesinBalancesofReceivablesandContractLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/NetProductSalesScheduleofChangesinBalancesofReceivablesandContractLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-7556-920a-4a47d0d998bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-7281-929c-380bb32a674a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-7556-920a-4a47d0d998bf" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-7281-929c-380bb32a674a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7b83-aaf6-2c1d3c865ce9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-7281-929c-380bb32a674a" xlink:to="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7b83-aaf6-2c1d3c865ce9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7b83-aaf6-2c1d3c865ce9_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7b83-aaf6-2c1d3c865ce9" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7b83-aaf6-2c1d3c865ce9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7905-911b-3b7aa3c332af" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-7b83-aaf6-2c1d3c865ce9" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7905-911b-3b7aa3c332af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ProductSalesMember_019c9a8b-980d-7704-9b9c-c5824db8667f" xlink:href="mrna-20260331.xsd#mrna_ProductSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7905-911b-3b7aa3c332af" xlink:to="loc_mrna_ProductSalesMember_019c9a8b-980d-7704-9b9c-c5824db8667f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ChangeInContractWithCustomerLiabilityRefundRollForward_019c9a8b-980d-7c1b-a8df-02d8d59a4af3" xlink:href="mrna-20260331.xsd#mrna_ChangeInContractWithCustomerLiabilityRefundRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-7556-920a-4a47d0d998bf" xlink:to="loc_mrna_ChangeInContractWithCustomerLiabilityRefundRollForward_019c9a8b-980d-7c1b-a8df-02d8d59a4af3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerRefundLiability_019c9a8b-980d-7e6f-896e-b67a8d4c7fd6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerRefundLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ChangeInContractWithCustomerLiabilityRefundRollForward_019c9a8b-980d-7c1b-a8df-02d8d59a4af3" xlink:to="loc_us-gaap_ContractWithCustomerRefundLiability_019c9a8b-980d-7e6f-896e-b67a8d4c7fd6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ContractWithCustomerLiabilityProvisionsMadeInCurrentYear_019c9a8b-980d-7b77-8156-153fd2fe27d1" xlink:href="mrna-20260331.xsd#mrna_ContractWithCustomerLiabilityProvisionsMadeInCurrentYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ChangeInContractWithCustomerLiabilityRefundRollForward_019c9a8b-980d-7c1b-a8df-02d8d59a4af3" xlink:to="loc_mrna_ContractWithCustomerLiabilityProvisionsMadeInCurrentYear_019c9a8b-980d-7b77-8156-153fd2fe27d1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ContractWithCustomerLiabilityProvisionsMadeInPriorYears_019c9a8b-980d-7ebb-bf80-7698ba12d67e" xlink:href="mrna-20260331.xsd#mrna_ContractWithCustomerLiabilityProvisionsMadeInPriorYears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ChangeInContractWithCustomerLiabilityRefundRollForward_019c9a8b-980d-7c1b-a8df-02d8d59a4af3" xlink:to="loc_mrna_ContractWithCustomerLiabilityProvisionsMadeInPriorYears_019c9a8b-980d-7ebb-bf80-7698ba12d67e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ContractWithCustomerLiabilityProvisionRelatedToSales_019c9a8b-980d-7532-b703-c52cb2db491f" xlink:href="mrna-20260331.xsd#mrna_ContractWithCustomerLiabilityProvisionRelatedToSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ChangeInContractWithCustomerLiabilityRefundRollForward_019c9a8b-980d-7c1b-a8df-02d8d59a4af3" xlink:to="loc_mrna_ContractWithCustomerLiabilityProvisionRelatedToSales_019c9a8b-980d-7532-b703-c52cb2db491f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ContractWithCustomerRefundLiabilityPaymentsAndReturnsRelatedToPriorPeriodSales_019c9a8b-980d-767f-8891-362d916fdc9a" xlink:href="mrna-20260331.xsd#mrna_ContractWithCustomerRefundLiabilityPaymentsAndReturnsRelatedToPriorPeriodSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ChangeInContractWithCustomerLiabilityRefundRollForward_019c9a8b-980d-7c1b-a8df-02d8d59a4af3" xlink:to="loc_mrna_ContractWithCustomerRefundLiabilityPaymentsAndReturnsRelatedToPriorPeriodSales_019c9a8b-980d-767f-8891-362d916fdc9a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerRefundLiability_019c9a8b-980d-785a-8f90-f6a01720b0e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerRefundLiability"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/OtherRevenueDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#OtherRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/OtherRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-7603-9b0f-58a891dafe08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-76f7-98f6-7b02601ea226" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-7603-9b0f-58a891dafe08" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-76f7-98f6-7b02601ea226" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9a8b-980d-724a-81dc-35818e9629d9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019c9a8b-980d-76f7-98f6-7b02601ea226" xlink:to="loc_srt_ProductOrServiceAxis_019c9a8b-980d-724a-81dc-35818e9629d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-724a-81dc-35818e9629d9_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-724a-81dc-35818e9629d9" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-724a-81dc-35818e9629d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7c58-96b0-2b18dd670ee9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-980d-724a-81dc-35818e9629d9" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7c58-96b0-2b18dd670ee9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_StandReadyManufacturingMember_019d4c45-2d6f-7c01-a0fe-90b6557acf27" xlink:href="mrna-20260331.xsd#mrna_StandReadyManufacturingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7c58-96b0-2b18dd670ee9" xlink:to="loc_mrna_StandReadyManufacturingMember_019d4c45-2d6f-7c01-a0fe-90b6557acf27" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_CollaborationArrangementIncludingArrangementsWithAffiliateMember_019c9a8b-980d-7662-921e-92506eca0dfb" xlink:href="mrna-20260331.xsd#mrna_CollaborationArrangementIncludingArrangementsWithAffiliateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7c58-96b0-2b18dd670ee9" xlink:to="loc_mrna_CollaborationArrangementIncludingArrangementsWithAffiliateMember_019c9a8b-980d-7662-921e-92506eca0dfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrantMember_019c9a8b-980d-7d57-b917-585f2d2ddd34" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7c58-96b0-2b18dd670ee9" xlink:to="loc_us-gaap_GrantMember_019c9a8b-980d-7d57-b917-585f2d2ddd34" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_LicenseAndRoyaltyMember_019c9a8b-980d-7f00-bda6-0e9284e3f701" xlink:href="mrna-20260331.xsd#mrna_LicenseAndRoyaltyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7c58-96b0-2b18dd670ee9" xlink:to="loc_mrna_LicenseAndRoyaltyMember_019c9a8b-980d-7f00-bda6-0e9284e3f701" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_019c9a8b-980d-7677-8038-32a89eb820bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-980d-7c58-96b0-2b18dd670ee9" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_019c9a8b-980d-7677-8038-32a89eb820bb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9a8b-980d-718e-9e2e-9881504d0007" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019c9a8b-980d-7603-9b0f-58a891dafe08" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9a8b-980d-718e-9e2e-9881504d0007" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/CollaborationAgreementsandResearchandDevelopmentFundingArrangementDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#CollaborationAgreementsandResearchandDevelopmentFundingArrangementDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/CollaborationAgreementsandResearchandDevelopmentFundingArrangementDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_019c9a8b-980d-76ce-9438-4af7b3cbe3c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_019c9a8b-980d-79b9-8f5e-3302651eae51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_019c9a8b-980d-76ce-9438-4af7b3cbe3c9" xlink:to="loc_us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_019c9a8b-980d-79b9-8f5e-3302651eae51" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019c9a8b-980d-7efd-a8ef-8478ee570221" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_019c9a8b-980d-79b9-8f5e-3302651eae51" xlink:to="loc_srt_CounterpartyNameAxis_019c9a8b-980d-7efd-a8ef-8478ee570221" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-980d-7efd-a8ef-8478ee570221_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019c9a8b-980d-7efd-a8ef-8478ee570221" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-980d-7efd-a8ef-8478ee570221_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-980d-7023-a6e4-1107d47e1e6c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019c9a8b-980d-7efd-a8ef-8478ee570221" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-980d-7023-a6e4-1107d47e1e6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_MerckMember_019c9a8b-980d-75f7-8682-6585b85f66a1" xlink:href="mrna-20260331.xsd#mrna_MerckMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-980d-7023-a6e4-1107d47e1e6c" xlink:to="loc_mrna_MerckMember_019c9a8b-980d-75f7-8682-6585b85f66a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_RecordatiS.p.AMember_019d7569-ed11-72b2-804a-5511d0bc4b3e" xlink:href="mrna-20260331.xsd#mrna_RecordatiS.p.AMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-980d-7023-a6e4-1107d47e1e6c" xlink:to="loc_mrna_RecordatiS.p.AMember_019d7569-ed11-72b2-804a-5511d0bc4b3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_BlackstoneLifeSciencesBlackstoneMember_019c9a8b-980d-71f5-b3f4-cf0a544b0a04" xlink:href="mrna-20260331.xsd#mrna_BlackstoneLifeSciencesBlackstoneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-980d-7023-a6e4-1107d47e1e6c" xlink:to="loc_mrna_BlackstoneLifeSciencesBlackstoneMember_019c9a8b-980d-71f5-b3f4-cf0a544b0a04" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfArrangementAxis_019c9a8b-980d-713b-a2b5-108337372070" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TypeOfArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_019c9a8b-980d-79b9-8f5e-3302651eae51" xlink:to="loc_us-gaap_TypeOfArrangementAxis_019c9a8b-980d-713b-a2b5-108337372070" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019c9a8b-980d-713b-a2b5-108337372070_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_019c9a8b-980d-713b-a2b5-108337372070" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019c9a8b-980d-713b-a2b5-108337372070_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019c9a8b-980d-7afd-94e0-e514e629b252" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_019c9a8b-980d-713b-a2b5-108337372070" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019c9a8b-980d-7afd-94e0-e514e629b252" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMember_019c9a8b-980d-7ede-bf13-0d3d6d8c0d67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019c9a8b-980d-7afd-94e0-e514e629b252" xlink:to="loc_us-gaap_CollaborativeArrangementTransactionWithPartyToCollaborativeArrangementMember_019c9a8b-980d-7ede-bf13-0d3d6d8c0d67" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ProceedsFromOptionExerciseFee_019c9a8b-980d-7f8c-8ed7-d39e1439dfe3" xlink:href="mrna-20260331.xsd#mrna_ProceedsFromOptionExerciseFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_019c9a8b-980d-76ce-9438-4af7b3cbe3c9" xlink:to="loc_mrna_ProceedsFromOptionExerciseFee_019c9a8b-980d-7f8c-8ed7-d39e1439dfe3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019c9a8b-980d-7041-aee1-291e8809158c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_019c9a8b-980d-76ce-9438-4af7b3cbe3c9" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019c9a8b-980d-7041-aee1-291e8809158c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_RecoveryOfCostsCapitalExpenditures_019c9a8b-980d-7a51-9ef8-d74e1f63292c" xlink:href="mrna-20260331.xsd#mrna_RecoveryOfCostsCapitalExpenditures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_019c9a8b-980d-76ce-9438-4af7b3cbe3c9" xlink:to="loc_mrna_RecoveryOfCostsCapitalExpenditures_019c9a8b-980d-7a51-9ef8-d74e1f63292c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress_019d756a-a538-7ed9-8d75-f2f00087cf05" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_019c9a8b-980d-76ce-9438-4af7b3cbe3c9" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress_019d756a-a538-7ed9-8d75-f2f00087cf05" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncome_019db13e-dbcc-78bd-b988-8e163336b406" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_019c9a8b-980d-76ce-9438-4af7b3cbe3c9" xlink:to="loc_us-gaap_DeferredIncome_019db13e-dbcc-78bd-b988-8e163336b406" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_CollaborativeArrangementRightsAndObligationsMaximumAggregateMilestonePayments_019db13d-e8ed-7cc7-91a2-48622d99f972" xlink:href="mrna-20260331.xsd#mrna_CollaborativeArrangementRightsAndObligationsMaximumAggregateMilestonePayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersLineItems_019c9a8b-980d-76ce-9438-4af7b3cbe3c9" xlink:to="loc_mrna_CollaborativeArrangementRightsAndObligationsMaximumAggregateMilestonePayments_019db13d-e8ed-7cc7-91a2-48622d99f972" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/FinancialInstrumentsScheduleofCashandAvailableforSaleSecuritiesbySignificantInvestmentCategoryDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#FinancialInstrumentsScheduleofCashandAvailableforSaleSecuritiesbySignificantInvestmentCategoryDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/FinancialInstrumentsScheduleofCashandAvailableforSaleSecuritiesbySignificantInvestmentCategoryDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7ed0-83cf-819dc6307464" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-75ee-b9fa-010a274195e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7ed0-83cf-819dc6307464" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-75ee-b9fa-010a274195e4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-715e-866e-1fbac9467b31" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-75ee-b9fa-010a274195e4" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-715e-866e-1fbac9467b31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-715e-866e-1fbac9467b31_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-715e-866e-1fbac9467b31" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-715e-866e-1fbac9467b31_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-74a2-854f-3344241a6090" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-715e-866e-1fbac9467b31" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-74a2-854f-3344241a6090" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_019c9a8b-980d-7354-a6a6-189c78a377cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-74a2-854f-3344241a6090" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_019c9a8b-980d-7354-a6a6-189c78a377cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_019c9a8b-980d-78e9-b6f1-4d8277467e23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-74a2-854f-3344241a6090" xlink:to="loc_us-gaap_CertificatesOfDepositMember_019c9a8b-980d-78e9-b6f1-4d8277467e23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_019c9a8b-980d-7240-8864-cfa968477065" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-74a2-854f-3344241a6090" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_019c9a8b-980d-7240-8864-cfa968477065" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_019c9a8b-980d-7381-8da4-6101f56d1f75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-74a2-854f-3344241a6090" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_019c9a8b-980d-7381-8da4-6101f56d1f75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019c9a8b-980d-7c14-8910-097e2ad9b9d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-74a2-854f-3344241a6090" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019c9a8b-980d-7c14-8910-097e2ad9b9d8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentDebtSecuritiesMember_019c9a8b-980d-739f-9bcc-7e6758e5e308" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-74a2-854f-3344241a6090" xlink:to="loc_us-gaap_USGovernmentDebtSecuritiesMember_019c9a8b-980d-739f-9bcc-7e6758e5e308" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_019c9a8b-980d-7083-8b6c-6f10a8d8add3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-75ee-b9fa-010a274195e4" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_019c9a8b-980d-7083-8b6c-6f10a8d8add3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019c9a8b-980d-7083-8b6c-6f10a8d8add3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019c9a8b-980d-7083-8b6c-6f10a8d8add3" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019c9a8b-980d-7083-8b6c-6f10a8d8add3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019c9a8b-980d-76a9-8233-6c5a27dd8ecf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019c9a8b-980d-7083-8b6c-6f10a8d8add3" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019c9a8b-980d-76a9-8233-6c5a27dd8ecf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsMember_019c9a8b-980d-713e-ae3d-8b9177c7cce6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019c9a8b-980d-76a9-8233-6c5a27dd8ecf" xlink:to="loc_us-gaap_CashAndCashEquivalentsMember_019c9a8b-980d-713e-ae3d-8b9177c7cce6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_CurrentMarketableSecuritiesMember_019c9a8b-980d-7a2f-aa39-232120be9a41" xlink:href="mrna-20260331.xsd#mrna_CurrentMarketableSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019c9a8b-980d-76a9-8233-6c5a27dd8ecf" xlink:to="loc_mrna_CurrentMarketableSecuritiesMember_019c9a8b-980d-7a2f-aa39-232120be9a41" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_NoncurrentMarketableSecuritiesMember_019c9a8b-980d-7328-a52e-5c0c12dd5db1" xlink:href="mrna-20260331.xsd#mrna_NoncurrentMarketableSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019c9a8b-980d-76a9-8233-6c5a27dd8ecf" xlink:to="loc_mrna_NoncurrentMarketableSecuritiesMember_019c9a8b-980d-7328-a52e-5c0c12dd5db1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9a8b-980d-736b-87a2-55533ebfa884" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-75ee-b9fa-010a274195e4" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9a8b-980d-736b-87a2-55533ebfa884" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-980d-736b-87a2-55533ebfa884_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9a8b-980d-736b-87a2-55533ebfa884" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-980d-736b-87a2-55533ebfa884_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-980d-7471-becc-ef6bb47fe0f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9a8b-980d-736b-87a2-55533ebfa884" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-980d-7471-becc-ef6bb47fe0f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019c9a8b-980d-79f2-9787-0c63be8927b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-980d-7471-becc-ef6bb47fe0f2" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019c9a8b-980d-79f2-9787-0c63be8927b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019c9a8b-980d-7eb0-98df-03d82f36f588" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-980d-7471-becc-ef6bb47fe0f2" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019c9a8b-980d-7eb0-98df-03d82f36f588" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019c9a8b-980d-7be6-9ae5-c9b24c14b4a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7ed0-83cf-819dc6307464" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_019c9a8b-980d-7be6-9ae5-c9b24c14b4a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019c9a8b-980d-70ce-ada1-2bc6bf5f4be9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7ed0-83cf-819dc6307464" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_019c9a8b-980d-70ce-ada1-2bc6bf5f4be9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019c9a8b-980d-7944-8c42-ffa06e7e969e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7ed0-83cf-819dc6307464" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_019c9a8b-980d-7944-8c42-ffa06e7e969e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019c9a8b-980d-7344-8010-210684091c0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7ed0-83cf-819dc6307464" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019c9a8b-980d-7344-8010-210684091c0b" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/FinancialInstrumentsScheduleofUnrealizedLossPositionDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#FinancialInstrumentsScheduleofUnrealizedLossPositionDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/FinancialInstrumentsScheduleofUnrealizedLossPositionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7f93-a28e-7b71d7df07e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-7230-8690-fe242087eb38" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7f93-a28e-7b71d7df07e7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-7230-8690-fe242087eb38" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-729d-8c5c-fc0b44bd7785" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-7230-8690-fe242087eb38" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-729d-8c5c-fc0b44bd7785" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-729d-8c5c-fc0b44bd7785_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-729d-8c5c-fc0b44bd7785" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-729d-8c5c-fc0b44bd7785_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-70ee-9975-425f39255d52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-729d-8c5c-fc0b44bd7785" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-70ee-9975-425f39255d52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryBillSecuritiesMember_019c9a8b-980d-7ea1-8cf0-793c54f1ae86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryBillSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-70ee-9975-425f39255d52" xlink:to="loc_us-gaap_USTreasuryBillSecuritiesMember_019c9a8b-980d-7ea1-8cf0-793c54f1ae86" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasuryNotesSecuritiesMember_019c9a8b-980d-766e-aa7f-3df7c7c10b88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasuryNotesSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-70ee-9975-425f39255d52" xlink:to="loc_us-gaap_USTreasuryNotesSecuritiesMember_019c9a8b-980d-766e-aa7f-3df7c7c10b88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019c9a8b-980d-7720-abf9-0d44adc644fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-70ee-9975-425f39255d52" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019c9a8b-980d-7720-abf9-0d44adc644fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentDebtSecuritiesMember_019c9a8b-980d-7275-b0da-7c2a2ee1e8b3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-70ee-9975-425f39255d52" xlink:to="loc_us-gaap_USGovernmentDebtSecuritiesMember_019c9a8b-980d-7275-b0da-7c2a2ee1e8b3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019c9a8b-980d-796e-9b63-b593bfcc1959" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7f93-a28e-7b71d7df07e7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019c9a8b-980d-796e-9b63-b593bfcc1959" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019c9a8b-980d-7668-948b-9e1d75f2c819" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7f93-a28e-7b71d7df07e7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019c9a8b-980d-7668-948b-9e1d75f2c819" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019c9a8b-980d-7e58-8420-961506240471" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7f93-a28e-7b71d7df07e7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019c9a8b-980d-7e58-8420-961506240471" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019c9a8b-980d-77d3-9165-85dcb067ca14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7f93-a28e-7b71d7df07e7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019c9a8b-980d-77d3-9165-85dcb067ca14" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019c9a8b-980d-75a9-85ae-20e0f1cbab28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7f93-a28e-7b71d7df07e7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019c9a8b-980d-75a9-85ae-20e0f1cbab28" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019c9a8b-980d-7f85-ba1e-27b34bd367b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-980d-7f93-a28e-7b71d7df07e7" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019c9a8b-980d-7f85-ba1e-27b34bd367b9" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/FinancialInstrumentsScheduleofFinancialAssetsMeasuredatFairValueonRecurringBasisDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#FinancialInstrumentsScheduleofFinancialAssetsMeasuredatFairValueonRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/FinancialInstrumentsScheduleofFinancialAssetsMeasuredatFairValueonRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-98bf-7204-8210-6e8941665693" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-7049-87a8-82f63f6bd3ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-98bf-7204-8210-6e8941665693" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-7049-87a8-82f63f6bd3ee" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019c9a8b-980d-7ab7-a774-2b29fc6454a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-7049-87a8-82f63f6bd3ee" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019c9a8b-980d-7ab7-a774-2b29fc6454a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019c9a8b-980d-7ab7-a774-2b29fc6454a0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019c9a8b-980d-7ab7-a774-2b29fc6454a0" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019c9a8b-980d-7ab7-a774-2b29fc6454a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019c9a8b-980d-7f0e-aa5f-ccde802e93a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019c9a8b-980d-7ab7-a774-2b29fc6454a0" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019c9a8b-980d-7f0e-aa5f-ccde802e93a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019c9a8b-980d-7ebd-9e7d-37429fca4209" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019c9a8b-980d-7f0e-aa5f-ccde802e93a8" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019c9a8b-980d-7ebd-9e7d-37429fca4209" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-78f2-9541-516227c3203a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-7049-87a8-82f63f6bd3ee" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-78f2-9541-516227c3203a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-78f2-9541-516227c3203a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-78f2-9541-516227c3203a" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-78f2-9541-516227c3203a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-7d18-8858-0a8699266882" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019c9a8b-980d-78f2-9541-516227c3203a" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-7d18-8858-0a8699266882" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_019c9a8b-980d-709a-9f89-654a099f32d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-7d18-8858-0a8699266882" xlink:to="loc_us-gaap_MoneyMarketFundsMember_019c9a8b-980d-709a-9f89-654a099f32d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_019c9a8b-980d-7572-8cfc-71393ad4f649" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-7d18-8858-0a8699266882" xlink:to="loc_us-gaap_CertificatesOfDepositMember_019c9a8b-980d-7572-8cfc-71393ad4f649" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_019c9a8b-980d-7364-b7df-17163418e6e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-7d18-8858-0a8699266882" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_019c9a8b-980d-7364-b7df-17163418e6e0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_019c9a8b-980d-72ce-af62-98004f857606" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-7d18-8858-0a8699266882" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_019c9a8b-980d-72ce-af62-98004f857606" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_019c9a8b-98bf-74ef-af32-c27b9647c49d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-7d18-8858-0a8699266882" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_019c9a8b-98bf-74ef-af32-c27b9647c49d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentDebtSecuritiesMember_019c9a8b-98bf-764d-a52e-90f4905cedf6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_USGovernmentDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-7d18-8858-0a8699266882" xlink:to="loc_us-gaap_USGovernmentDebtSecuritiesMember_019c9a8b-98bf-764d-a52e-90f4905cedf6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesMember_019c9a8b-98bf-78be-b76a-9414050c50e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019c9a8b-980d-7d18-8858-0a8699266882" xlink:to="loc_us-gaap_EquitySecuritiesMember_019c9a8b-98bf-78be-b76a-9414050c50e6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9a8b-98bf-7d85-984e-d67754773bbe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019c9a8b-980d-7049-87a8-82f63f6bd3ee" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9a8b-98bf-7d85-984e-d67754773bbe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-98bf-7d85-984e-d67754773bbe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9a8b-98bf-7d85-984e-d67754773bbe" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-98bf-7d85-984e-d67754773bbe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-98bf-7fc9-8ec2-3938adecd0c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9a8b-98bf-7d85-984e-d67754773bbe" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-98bf-7fc9-8ec2-3938adecd0c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019c9a8b-98bf-74ef-8605-43248018488c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-98bf-7fc9-8ec2-3938adecd0c4" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019c9a8b-98bf-74ef-8605-43248018488c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019c9a8b-98bf-78e4-b6d0-c3537ea45d97" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9a8b-98bf-7fc9-8ec2-3938adecd0c4" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019c9a8b-98bf-78e4-b6d0-c3537ea45d97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019c9a8b-98bf-736d-bf68-4b0cae23b2ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-98bf-7204-8210-6e8941665693" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019c9a8b-98bf-736d-bf68-4b0cae23b2ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019c9a8b-98bf-7cbe-9ee6-b730dc120794" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-98bf-7204-8210-6e8941665693" xlink:to="loc_us-gaap_DerivativeAssets_019c9a8b-98bf-7cbe-9ee6-b730dc120794" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019c9a8b-98bf-7256-9bfd-654f71f9ced2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-98bf-7204-8210-6e8941665693" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019c9a8b-98bf-7256-9bfd-654f71f9ced2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019c9a8b-98bf-7869-bb6e-8fc79789bd93" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019c9a8b-98bf-7204-8210-6e8941665693" xlink:to="loc_us-gaap_DerivativeLiabilities_019c9a8b-98bf-7869-bb6e-8fc79789bd93" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/InventoryNarrativeDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#InventoryNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/InventoryNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryLineItems_019c9a8b-98bf-77ee-86d2-4d1af56693f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryCurrentTable_019c9a8b-98bf-74c5-8c5c-0a5f34f18ce3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryCurrentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_InventoryLineItems_019c9a8b-98bf-77ee-86d2-4d1af56693f3" xlink:to="loc_us-gaap_InventoryCurrentTable_019c9a8b-98bf-74c5-8c5c-0a5f34f18ce3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019c9a8b-98bf-777d-9709-b98eab1d4569" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InventoryCurrentTable_019c9a8b-98bf-74c5-8c5c-0a5f34f18ce3" xlink:to="loc_srt_RangeAxis_019c9a8b-98bf-777d-9709-b98eab1d4569" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c9a8b-98bf-777d-9709-b98eab1d4569_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019c9a8b-98bf-777d-9709-b98eab1d4569" xlink:to="loc_srt_RangeMember_019c9a8b-98bf-777d-9709-b98eab1d4569_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c9a8b-98bf-7df0-8b3a-2a10fdaa4988" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019c9a8b-98bf-777d-9709-b98eab1d4569" xlink:to="loc_srt_RangeMember_019c9a8b-98bf-7df0-8b3a-2a10fdaa4988" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019c9a8b-98bf-7c24-9fcc-39600c272b98" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c9a8b-98bf-7df0-8b3a-2a10fdaa4988" xlink:to="loc_srt_MinimumMember_019c9a8b-98bf-7c24-9fcc-39600c272b98" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019c9a8b-98bf-79e5-9055-b796ef9d0649" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c9a8b-98bf-7df0-8b3a-2a10fdaa4988" xlink:to="loc_srt_MaximumMember_019c9a8b-98bf-79e5-9055-b796ef9d0649" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryAxis_019c9a8b-98bf-7739-ae0e-bc33a75c5778" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PublicUtilitiesInventoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InventoryCurrentTable_019c9a8b-98bf-74c5-8c5c-0a5f34f18ce3" xlink:to="loc_us-gaap_PublicUtilitiesInventoryAxis_019c9a8b-98bf-7739-ae0e-bc33a75c5778" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_019c9a8b-98bf-7739-ae0e-bc33a75c5778_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_019c9a8b-98bf-7739-ae0e-bc33a75c5778" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_019c9a8b-98bf-7739-ae0e-bc33a75c5778_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_019c9a8b-98bf-7566-b67a-549d506b23d0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PublicUtilitiesInventoryTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PublicUtilitiesInventoryAxis_019c9a8b-98bf-7739-ae0e-bc33a75c5778" xlink:to="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_019c9a8b-98bf-7566-b67a-549d506b23d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_COVIDVaccineMember_019c9a8b-98bf-7aee-9775-bb0c2a33f00b" xlink:href="mrna-20260331.xsd#mrna_COVIDVaccineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_019c9a8b-98bf-7566-b67a-549d506b23d0" xlink:to="loc_mrna_COVIDVaccineMember_019c9a8b-98bf-7aee-9775-bb0c2a33f00b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_MNEXSPIKEVaccineMember_019c9a8b-98bf-7fbf-b7f5-64442e424f17" xlink:href="mrna-20260331.xsd#mrna_MNEXSPIKEVaccineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_019c9a8b-98bf-7566-b67a-549d506b23d0" xlink:to="loc_mrna_MNEXSPIKEVaccineMember_019c9a8b-98bf-7fbf-b7f5-64442e424f17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_RSVVaccineMember_019c9a8b-98bf-79d6-a237-a3726f7c8137" xlink:href="mrna-20260331.xsd#mrna_RSVVaccineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesInventoryTypeDomain_019c9a8b-98bf-7566-b67a-549d506b23d0" xlink:to="loc_mrna_RSVVaccineMember_019c9a8b-98bf-79d6-a237-a3726f7c8137" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWriteDown_019c9a8b-98bf-7f34-947d-4d7300e4f458" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryWriteDown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_019c9a8b-98bf-77ee-86d2-4d1af56693f3" xlink:to="loc_us-gaap_InventoryWriteDown_019c9a8b-98bf-7f34-947d-4d7300e4f458" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryFirmPurchaseCommitmentLoss_019c9a8b-98bf-7e0e-8bee-1e2432ca0273" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryFirmPurchaseCommitmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_019c9a8b-98bf-77ee-86d2-4d1af56693f3" xlink:to="loc_us-gaap_InventoryFirmPurchaseCommitmentLoss_019c9a8b-98bf-7e0e-8bee-1e2432ca0273" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryGross_019c9a8b-98bf-7e05-b43f-a0c83d6db4ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_019c9a8b-98bf-77ee-86d2-4d1af56693f3" xlink:to="loc_us-gaap_InventoryGross_019c9a8b-98bf-7e05-b43f-a0c83d6db4ac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_InventoryShelfLife_019c9a8b-98bf-7c7f-b0f3-2ae657b45ce7" xlink:href="mrna-20260331.xsd#mrna_InventoryShelfLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InventoryLineItems_019c9a8b-98bf-77ee-86d2-4d1af56693f3" xlink:to="loc_mrna_InventoryShelfLife_019c9a8b-98bf-7c7f-b0f3-2ae657b45ce7" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/PropertyPlantandEquipmentNetScheduleofPropertyandEquipmentNetDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#PropertyPlantandEquipmentNetScheduleofPropertyandEquipmentNetDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/PropertyPlantandEquipmentNetScheduleofPropertyandEquipmentNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019c9a8b-98bf-72bc-8017-c38d0e5247f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019c9a8b-98bf-77c5-8214-dddb52881852" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019c9a8b-98bf-72bc-8017-c38d0e5247f8" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019c9a8b-98bf-77c5-8214-dddb52881852" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019c9a8b-98bf-7499-ac0a-a1f0db00b308" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019c9a8b-98bf-77c5-8214-dddb52881852" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019c9a8b-98bf-7499-ac0a-a1f0db00b308" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7499-ac0a-a1f0db00b308_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019c9a8b-98bf-7499-ac0a-a1f0db00b308" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7499-ac0a-a1f0db00b308_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019c9a8b-98bf-7499-ac0a-a1f0db00b308" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandMember_019c9a8b-98bf-785e-bd85-b84877401fa3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:to="loc_us-gaap_LandMember_019c9a8b-98bf-785e-bd85-b84877401fa3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingAndBuildingImprovementsMember_019c9a8b-98bf-7581-a670-e1b12a1c0528" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BuildingAndBuildingImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:to="loc_us-gaap_BuildingAndBuildingImprovementsMember_019c9a8b-98bf-7581-a670-e1b12a1c0528" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquipmentMember_019c9a8b-98bf-78b9-a1c7-6700df0732dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:to="loc_us-gaap_EquipmentMember_019c9a8b-98bf-78b9-a1c7-6700df0732dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_019c9a8b-98bf-748f-b581-5779ffc82cb4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_019c9a8b-98bf-748f-b581-5779ffc82cb4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentOtherTypesMember_019c9a8b-98bf-76b9-8116-f9ca689873f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentOtherTypesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentOtherTypesMember_019c9a8b-98bf-76b9-8116-f9ca689873f3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_019c9a8b-98bf-757e-a829-bb4dae42bf8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:to="loc_us-gaap_ComputerEquipmentMember_019c9a8b-98bf-757e-a829-bb4dae42bf8e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_019c9a8b-98bf-7844-ad9d-417db66046fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:to="loc_us-gaap_ConstructionInProgressMember_019c9a8b-98bf-7844-ad9d-417db66046fd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_FinancingRightOfUseAssetMember_019c9a8b-98bf-7684-8d48-0af168824c08" xlink:href="mrna-20260331.xsd#mrna_FinancingRightOfUseAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019c9a8b-98bf-7a43-937e-dc8ef86c1b6e" xlink:to="loc_mrna_FinancingRightOfUseAssetMember_019c9a8b-98bf-7684-8d48-0af168824c08" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019c9a8b-98bf-760c-a773-2b2571cbc2ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019c9a8b-98bf-72bc-8017-c38d0e5247f8" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_019c9a8b-98bf-760c-a773-2b2571cbc2ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019c9a8b-98bf-74bf-8032-37d8434f5087" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019c9a8b-98bf-72bc-8017-c38d0e5247f8" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_019c9a8b-98bf-74bf-8032-37d8434f5087" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019c9a8b-98bf-7660-b037-2e1d59ff3220" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019c9a8b-98bf-72bc-8017-c38d0e5247f8" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_019c9a8b-98bf-7660-b037-2e1d59ff3220" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/OtherBalanceSheetComponentsScheduleofOtherNonCurrentAssetsDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#OtherBalanceSheetComponentsScheduleofOtherNonCurrentAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/OtherBalanceSheetComponentsScheduleofOtherNonCurrentAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019dc249-cd6b-761f-8dee-9f711eda2d7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019dc249-cd6b-761f-8dee-9f711eda2d7a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_019dc24a-b3da-79c4-b3ae-d7bc1b1a578f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019dc249-cd6b-761f-8dee-9f711eda2d7a" xlink:to="loc_srt_LitigationCaseAxis_019dc24a-b3da-79c4-b3ae-d7bc1b1a578f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019dc24a-b3da-79c4-b3ae-d7bc1b1a578f_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_019dc24a-b3da-79c4-b3ae-d7bc1b1a578f" xlink:to="loc_srt_LitigationCaseTypeDomain_019dc24a-b3da-79c4-b3ae-d7bc1b1a578f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019dc24a-b3da-7a41-9fb2-f612964d7c98" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_019dc24a-b3da-79c4-b3ae-d7bc1b1a578f" xlink:to="loc_srt_LitigationCaseTypeDomain_019dc24a-b3da-7a41-9fb2-f612964d7c98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ArbutusBiopharmaCorporationArbutusAndGenevantSciencesGmbHGenevantMember_019dc24a-b3da-71d1-83a8-06502f395cfd" xlink:href="mrna-20260331.xsd#mrna_ArbutusBiopharmaCorporationArbutusAndGenevantSciencesGmbHGenevantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019dc24a-b3da-7a41-9fb2-f612964d7c98" xlink:to="loc_mrna_ArbutusBiopharmaCorporationArbutusAndGenevantSciencesGmbHGenevantMember_019dc24a-b3da-71d1-83a8-06502f395cfd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019dc24a-b3da-7230-9e51-029e23835834" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019dc249-cd6b-761f-8dee-9f711eda2d7a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019dc24a-b3da-7230-9e51-029e23835834" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dc24a-b3da-7230-9e51-029e23835834_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019dc24a-b3da-7230-9e51-029e23835834" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dc24a-b3da-7230-9e51-029e23835834_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dc24a-b3da-73eb-b137-4bf9333b9ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019dc24a-b3da-7230-9e51-029e23835834" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dc24a-b3da-73eb-b137-4bf9333b9ff3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntellectualPropertyMember_019dc24a-b3da-7b02-96cf-b5a6ffcd7606" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntellectualPropertyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019dc24a-b3da-73eb-b137-4bf9333b9ff3" xlink:to="loc_us-gaap_IntellectualPropertyMember_019dc24a-b3da-7b02-96cf-b5a6ffcd7606" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesReceivableNoncurrent_019c9a8b-98bf-7218-83c2-b6729adf21db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxesReceivableNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:to="loc_us-gaap_IncomeTaxesReceivableNoncurrent_019c9a8b-98bf-7218-83c2-b6729adf21db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNoncurrent_019c9a8b-98bf-7188-807c-0d1a259f9cbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InventoryNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:to="loc_us-gaap_InventoryNoncurrent_019c9a8b-98bf-7188-807c-0d1a259f9cbc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019c9a8b-98bf-716b-9eb3-118a62cb1736" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019c9a8b-98bf-716b-9eb3-118a62cb1736" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DownpaymentsAndPrepaymentsNoncurrent_019c9a8b-98bf-7e9c-a423-70b50e5baed2" xlink:href="mrna-20260331.xsd#mrna_DownpaymentsAndPrepaymentsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:to="loc_mrna_DownpaymentsAndPrepaymentsNoncurrent_019c9a8b-98bf-7e9c-a423-70b50e5baed2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_019c9a8b-98bf-7466-aa5a-ec4d6cb4a91e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_019c9a8b-98bf-7466-aa5a-ec4d6cb4a91e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019c9a8b-98bf-7642-a92e-0bfc4f2fda5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:to="loc_us-gaap_Goodwill_019c9a8b-98bf-7642-a92e-0bfc4f2fda5c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_019c9a8b-98bf-7fe0-8c63-399cae57d294" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsMiscellaneousNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:to="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_019c9a8b-98bf-7fe0-8c63-399cae57d294" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019c9a8b-98bf-7cc9-99ab-9d8feb139773" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019dc24a-11f5-7416-9989-978ffe67d1bb" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_019c9a8b-98bf-7cc9-99ab-9d8feb139773" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/OtherBalanceSheetComponentsScheduleofDeferredRevenueDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#OtherBalanceSheetComponentsScheduleofDeferredRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/OtherBalanceSheetComponentsScheduleofDeferredRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ChangeInContractWithCustomerLiabilityLineItems_019c9a8b-98bf-7210-af43-cf2bd231ccff" xlink:href="mrna-20260331.xsd#mrna_ChangeInContractWithCustomerLiabilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ChangeInContractWithCustomerLiabilityTable_019c9a8b-98bf-7bf0-b520-c9a71a6261d1" xlink:href="mrna-20260331.xsd#mrna_ChangeInContractWithCustomerLiabilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_mrna_ChangeInContractWithCustomerLiabilityLineItems_019c9a8b-98bf-7210-af43-cf2bd231ccff" xlink:to="loc_mrna_ChangeInContractWithCustomerLiabilityTable_019c9a8b-98bf-7bf0-b520-c9a71a6261d1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9a8b-98bf-7bea-bc95-f56656f30a3a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_mrna_ChangeInContractWithCustomerLiabilityTable_019c9a8b-98bf-7bf0-b520-c9a71a6261d1" xlink:to="loc_srt_ProductOrServiceAxis_019c9a8b-98bf-7bea-bc95-f56656f30a3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-98bf-7bea-bc95-f56656f30a3a_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-98bf-7bea-bc95-f56656f30a3a" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-98bf-7bea-bc95-f56656f30a3a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9a8b-98bf-7ada-8a07-d3559231471d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9a8b-98bf-7bea-bc95-f56656f30a3a" xlink:to="loc_srt_ProductsAndServicesDomain_019c9a8b-98bf-7ada-8a07-d3559231471d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductAndServiceOtherMember_019c9a8b-98bf-7e95-9b99-d210e32f69cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductAndServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-98bf-7ada-8a07-d3559231471d" xlink:to="loc_us-gaap_ProductAndServiceOtherMember_019c9a8b-98bf-7e95-9b99-d210e32f69cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ProductSalesMember_019c9a8b-98bf-78e7-9244-7e7debacb9cf" xlink:href="mrna-20260331.xsd#mrna_ProductSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9a8b-98bf-7ada-8a07-d3559231471d" xlink:to="loc_mrna_ProductSalesMember_019c9a8b-98bf-78e7-9244-7e7debacb9cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ChangeInContractwithCustomerLiabilityRollForward_019c9a8b-98bf-745b-a2f9-2fc939fa5b0a" xlink:href="mrna-20260331.xsd#mrna_ChangeInContractwithCustomerLiabilityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ChangeInContractWithCustomerLiabilityLineItems_019c9a8b-98bf-7210-af43-cf2bd231ccff" xlink:to="loc_mrna_ChangeInContractwithCustomerLiabilityRollForward_019c9a8b-98bf-745b-a2f9-2fc939fa5b0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019c9a8b-98bf-720c-a24a-29d2f529bf2e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ChangeInContractwithCustomerLiabilityRollForward_019c9a8b-98bf-745b-a2f9-2fc939fa5b0a" xlink:to="loc_us-gaap_ContractWithCustomerLiability_019c9a8b-98bf-720c-a24a-29d2f529bf2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress_019c9a8b-98bf-70ba-8a66-9d3b0a2c3784" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ChangeInContractwithCustomerLiabilityRollForward_019c9a8b-98bf-745b-a2f9-2fc939fa5b0a" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCumulativeCatchUpAdjustmentToRevenueChangeInMeasureOfProgress_019c9a8b-98bf-70ba-8a66-9d3b0a2c3784" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ContractWithCustomerLiabilityDeductionsDuringPeriod_019c9a8b-98bf-73db-ac58-0fbb90e20334" xlink:href="mrna-20260331.xsd#mrna_ContractWithCustomerLiabilityDeductionsDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_ChangeInContractwithCustomerLiabilityRollForward_019c9a8b-98bf-745b-a2f9-2fc939fa5b0a" xlink:to="loc_mrna_ContractWithCustomerLiabilityDeductionsDuringPeriod_019c9a8b-98bf-73db-ac58-0fbb90e20334" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_019c9a8b-98bf-7a40-aa2b-ce3979e17755" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiability"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/LeasesNarrativeDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#LeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/LeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-7b8c-b425-da0df789ba09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_019c9a8b-98bf-71da-af85-3ead8ba275a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-7b8c-b425-da0df789ba09" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_019c9a8b-98bf-71da-af85-3ead8ba275a3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019c9a8b-98bf-737c-a9c7-db94cfc94590" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_019c9a8b-98bf-71da-af85-3ead8ba275a3" xlink:to="loc_srt_StatementGeographicalAxis_019c9a8b-98bf-737c-a9c7-db94cfc94590" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019c9a8b-98bf-737c-a9c7-db94cfc94590_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019c9a8b-98bf-737c-a9c7-db94cfc94590" xlink:to="loc_srt_SegmentGeographicalDomain_019c9a8b-98bf-737c-a9c7-db94cfc94590_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019c9a8b-98bf-7297-936d-5e86e7779645" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019c9a8b-98bf-737c-a9c7-db94cfc94590" xlink:to="loc_srt_SegmentGeographicalDomain_019c9a8b-98bf-7297-936d-5e86e7779645" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_CambridgeMassachusettsMember_019c9a8b-98bf-739a-94e7-fc68928f4513" xlink:href="mrna-20260331.xsd#mrna_CambridgeMassachusettsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019c9a8b-98bf-7297-936d-5e86e7779645" xlink:to="loc_mrna_CambridgeMassachusettsMember_019c9a8b-98bf-739a-94e7-fc68928f4513" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AreaOfRealEstateProperty_019c9a8b-98bf-752f-ac2c-4a1e77828d57" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AreaOfRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-7b8c-b425-da0df789ba09" xlink:to="loc_us-gaap_AreaOfRealEstateProperty_019c9a8b-98bf-752f-ac2c-4a1e77828d57" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_019c9a8b-98bf-77ca-a481-33cea841f48a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-7b8c-b425-da0df789ba09" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_019c9a8b-98bf-77ca-a481-33cea841f48a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_LesseeOperatingLeaseNumberOfExtensions_019c9a8b-98bf-7a7c-97ff-97cf234e9c61" xlink:href="mrna-20260331.xsd#mrna_LesseeOperatingLeaseNumberOfExtensions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-7b8c-b425-da0df789ba09" xlink:to="loc_mrna_LesseeOperatingLeaseNumberOfExtensions_019c9a8b-98bf-7a7c-97ff-97cf234e9c61" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_019c9a8b-98bf-7979-919e-fc4c9cef195c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-7b8c-b425-da0df789ba09" xlink:to="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_019c9a8b-98bf-7979-919e-fc4c9cef195c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/CreditAgreementDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#CreditAgreementDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/CreditAgreementDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019d4c4f-5528-7c75-aa87-9796371c82da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:to="loc_us-gaap_DebtInstrumentTable_019d4c4f-5528-7c75-aa87-9796371c82da" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019d4c4f-5528-75d1-b31f-f836e0742cbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019d4c4f-5528-7c75-aa87-9796371c82da" xlink:to="loc_us-gaap_CreditFacilityAxis_019d4c4f-5528-75d1-b31f-f836e0742cbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019d4c4f-5528-75d1-b31f-f836e0742cbf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019d4c4f-5528-75d1-b31f-f836e0742cbf" xlink:to="loc_us-gaap_CreditFacilityDomain_019d4c4f-5528-75d1-b31f-f836e0742cbf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019d4c4f-5528-7a00-98e7-0ffe5e91e829" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019d4c4f-5528-75d1-b31f-f836e0742cbf" xlink:to="loc_us-gaap_CreditFacilityDomain_019d4c4f-5528-7a00-98e7-0ffe5e91e829" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019d4c4f-5528-7b3b-bcd2-d5debbc2a22f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019d4c4f-5528-7a00-98e7-0ffe5e91e829" xlink:to="loc_us-gaap_SecuredDebtMember_019d4c4f-5528-7b3b-bcd2-d5debbc2a22f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019d4c4f-5528-7526-9440-e9ebdb90ec38" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019d4c4f-5528-7c75-aa87-9796371c82da" xlink:to="loc_us-gaap_DebtInstrumentAxis_019d4c4f-5528-7526-9440-e9ebdb90ec38" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019d4c4f-5528-7526-9440-e9ebdb90ec38_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019d4c4f-5528-7526-9440-e9ebdb90ec38" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019d4c4f-5528-7526-9440-e9ebdb90ec38_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019d4c4f-5528-721d-ae92-d5e4191a421d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019d4c4f-5528-7526-9440-e9ebdb90ec38" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019d4c4f-5528-721d-ae92-d5e4191a421d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_InitialTermLoanMember_019d4c4f-5528-7b0e-9243-b423cc662567" xlink:href="mrna-20260331.xsd#mrna_InitialTermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019d4c4f-5528-721d-ae92-d5e4191a421d" xlink:to="loc_mrna_InitialTermLoanMember_019d4c4f-5528-7b0e-9243-b423cc662567" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DelayedDrawTermLoanFacilityMember_019d4c4f-5528-72d8-a220-0e356efd43a7" xlink:href="mrna-20260331.xsd#mrna_DelayedDrawTermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019d4c4f-5528-721d-ae92-d5e4191a421d" xlink:to="loc_mrna_DelayedDrawTermLoanFacilityMember_019d4c4f-5528-72d8-a220-0e356efd43a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DelayedDrawTermLoanFacility1Member_019d4c4f-5528-7838-8461-40fd0c639534" xlink:href="mrna-20260331.xsd#mrna_DelayedDrawTermLoanFacility1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_DelayedDrawTermLoanFacilityMember_019d4c4f-5528-72d8-a220-0e356efd43a7" xlink:to="loc_mrna_DelayedDrawTermLoanFacility1Member_019d4c4f-5528-7838-8461-40fd0c639534" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DelayedDrawTermLoanFacility2Member_019d4c4f-5529-7f88-9ef6-1aecbfba570f" xlink:href="mrna-20260331.xsd#mrna_DelayedDrawTermLoanFacility2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_DelayedDrawTermLoanFacilityMember_019d4c4f-5528-72d8-a220-0e356efd43a7" xlink:to="loc_mrna_DelayedDrawTermLoanFacility2Member_019d4c4f-5529-7f88-9ef6-1aecbfba570f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019d4c4f-5529-7a96-af7c-7106469270eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019d4c4f-5528-7c75-aa87-9796371c82da" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019d4c4f-5529-7a96-af7c-7106469270eb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019d4c4f-5529-7a96-af7c-7106469270eb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019d4c4f-5529-7a96-af7c-7106469270eb" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019d4c4f-5529-7a96-af7c-7106469270eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019d4c4f-5529-757a-87ee-c2c0ed39576c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019d4c4f-5529-7a96-af7c-7106469270eb" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019d4c4f-5529-757a-87ee-c2c0ed39576c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019d4c4f-5529-7b5d-8735-5d4d038854b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019d4c4f-5529-757a-87ee-c2c0ed39576c" xlink:to="loc_us-gaap_LineOfCreditMember_019d4c4f-5529-7b5d-8735-5d4d038854b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_019d4c4f-5529-7572-b9d2-d442cde64a58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019d4c4f-5528-7c75-aa87-9796371c82da" xlink:to="loc_us-gaap_VariableRateAxis_019d4c4f-5529-7572-b9d2-d442cde64a58" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019d4c4f-5529-7572-b9d2-d442cde64a58_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_019d4c4f-5529-7572-b9d2-d442cde64a58" xlink:to="loc_us-gaap_VariableRateDomain_019d4c4f-5529-7572-b9d2-d442cde64a58_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019d4c4f-5529-7bf5-868e-7b447f84d9c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_019d4c4f-5529-7572-b9d2-d442cde64a58" xlink:to="loc_us-gaap_VariableRateDomain_019d4c4f-5529-7bf5-868e-7b447f84d9c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019d4c4f-5529-7480-946f-b2d0fb50bda8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019d4c4f-5529-7bf5-868e-7b447f84d9c4" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019d4c4f-5529-7480-946f-b2d0fb50bda8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BaseRateMember_019d4c4f-5529-74aa-88da-d5d304ca75f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BaseRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019d4c4f-5529-7bf5-868e-7b447f84d9c4" xlink:to="loc_us-gaap_BaseRateMember_019d4c4f-5529-74aa-88da-d5d304ca75f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsEffectiveSwapRateMember_019d4c4f-5529-7f3d-b91b-bb9a779cf81e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalFundsEffectiveSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019d4c4f-5529-7bf5-868e-7b447f84d9c4" xlink:to="loc_us-gaap_FederalFundsEffectiveSwapRateMember_019d4c4f-5529-7f3d-b91b-bb9a779cf81e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_TermSecuredOvernightFinancingRatePlusMember_019d4c4f-5529-7052-b611-1ed8a6b24418" xlink:href="mrna-20260331.xsd#mrna_TermSecuredOvernightFinancingRatePlusMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019d4c4f-5529-7bf5-868e-7b447f84d9c4" xlink:to="loc_mrna_TermSecuredOvernightFinancingRatePlusMember_019d4c4f-5529-7052-b611-1ed8a6b24418" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DebtInstrumentCovenantComplianceScenarioAxis_019d4c4f-5529-769e-9c33-20808878d8ab" xlink:href="mrna-20260331.xsd#mrna_DebtInstrumentCovenantComplianceScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019d4c4f-5528-7c75-aa87-9796371c82da" xlink:to="loc_mrna_DebtInstrumentCovenantComplianceScenarioAxis_019d4c4f-5529-769e-9c33-20808878d8ab" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DebtInstrumentCovenantComplianceScenarioDomain_019d4c4f-5529-769e-9c33-20808878d8ab_default" xlink:href="mrna-20260331.xsd#mrna_DebtInstrumentCovenantComplianceScenarioDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_mrna_DebtInstrumentCovenantComplianceScenarioAxis_019d4c4f-5529-769e-9c33-20808878d8ab" xlink:to="loc_mrna_DebtInstrumentCovenantComplianceScenarioDomain_019d4c4f-5529-769e-9c33-20808878d8ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DebtInstrumentCovenantComplianceScenarioDomain_019d4c4f-5529-7a79-86d1-d2e2e30eaefc" xlink:href="mrna-20260331.xsd#mrna_DebtInstrumentCovenantComplianceScenarioDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_mrna_DebtInstrumentCovenantComplianceScenarioAxis_019d4c4f-5529-769e-9c33-20808878d8ab" xlink:to="loc_mrna_DebtInstrumentCovenantComplianceScenarioDomain_019d4c4f-5529-7a79-86d1-d2e2e30eaefc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_CovenantComplianceScenario1Member_019d4c4f-5529-7b5b-9338-e63f6ba9a98b" xlink:href="mrna-20260331.xsd#mrna_CovenantComplianceScenario1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_DebtInstrumentCovenantComplianceScenarioDomain_019d4c4f-5529-7a79-86d1-d2e2e30eaefc" xlink:to="loc_mrna_CovenantComplianceScenario1Member_019d4c4f-5529-7b5b-9338-e63f6ba9a98b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_CovenantComplianceScenario2Member_019d4c4f-5529-7d04-bb3f-c30880752c47" xlink:href="mrna-20260331.xsd#mrna_CovenantComplianceScenario2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_mrna_DebtInstrumentCovenantComplianceScenarioDomain_019d4c4f-5529-7a79-86d1-d2e2e30eaefc" xlink:to="loc_mrna_CovenantComplianceScenario2Member_019d4c4f-5529-7d04-bb3f-c30880752c47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019d4c4f-5529-7e3e-8fdd-4972c8617777" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019d4c4f-5529-7e3e-8fdd-4972c8617777" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019d4c4f-5529-7e2d-b220-6ea7138bdb0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019d4c4f-5529-7e2d-b220-6ea7138bdb0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019d4c4f-5529-7362-8828-7b1b57981972" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019d4c4f-5529-7362-8828-7b1b57981972" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DebtInstrumentCovenantComplianceMinimumCashAndCashEquivalents_019d4c4f-5529-7161-b48c-808a94c81a0c" xlink:href="mrna-20260331.xsd#mrna_DebtInstrumentCovenantComplianceMinimumCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:to="loc_mrna_DebtInstrumentCovenantComplianceMinimumCashAndCashEquivalents_019d4c4f-5529-7161-b48c-808a94c81a0c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DebtInstrumentCovenantComplianceAverageMarketCapitalizationTrailingPeriod_019d4c4f-5529-7aca-bee3-dee67f900042" xlink:href="mrna-20260331.xsd#mrna_DebtInstrumentCovenantComplianceAverageMarketCapitalizationTrailingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:to="loc_mrna_DebtInstrumentCovenantComplianceAverageMarketCapitalizationTrailingPeriod_019d4c4f-5529-7aca-bee3-dee67f900042" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_019d4c4f-5529-7534-bc39-0031347e7dd4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:to="loc_us-gaap_LineOfCredit_019d4c4f-5529-7534-bc39-0031347e7dd4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_DebtInstrumentCovenantComplianceAverageMarketCapitalization_019d4c4f-5529-738b-a9aa-b234e7cf7e59" xlink:href="mrna-20260331.xsd#mrna_DebtInstrumentCovenantComplianceAverageMarketCapitalization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:to="loc_mrna_DebtInstrumentCovenantComplianceAverageMarketCapitalization_019d4c4f-5529-738b-a9aa-b234e7cf7e59" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019d4c4f-5529-765f-bc3e-b83df6fa94c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019d4c4f-5529-7708-98bb-eb7b08db7277" xlink:to="loc_us-gaap_LongTermDebt_019d4c4f-5529-765f-bc3e-b83df6fa94c3" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/CommitmentsandContingenciesLegalProceedingsDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#CommitmentsandContingenciesLegalProceedingsDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/CommitmentsandContingenciesLegalProceedingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-7a15-b65a-caab7f08ad4e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019c9a8b-98bf-7d35-a62a-430cf650f499" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-7a15-b65a-caab7f08ad4e" xlink:to="loc_us-gaap_LossContingenciesTable_019c9a8b-98bf-7d35-a62a-430cf650f499" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_019d759d-8c3c-7703-aa9e-d17332288e0f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019c9a8b-98bf-7d35-a62a-430cf650f499" xlink:to="loc_srt_LitigationCaseAxis_019d759d-8c3c-7703-aa9e-d17332288e0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019d759d-8c3c-7703-aa9e-d17332288e0f_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_019d759d-8c3c-7703-aa9e-d17332288e0f" xlink:to="loc_srt_LitigationCaseTypeDomain_019d759d-8c3c-7703-aa9e-d17332288e0f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019d759d-8c3c-7e1b-8bd2-c27a523562e0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_019d759d-8c3c-7703-aa9e-d17332288e0f" xlink:to="loc_srt_LitigationCaseTypeDomain_019d759d-8c3c-7e1b-8bd2-c27a523562e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ArbutusBiopharmaCorporationArbutusAndGenevantSciencesGmbHGenevantMember_019d7591-7882-7230-a91c-755761fcebad" xlink:href="mrna-20260331.xsd#mrna_ArbutusBiopharmaCorporationArbutusAndGenevantSciencesGmbHGenevantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019d759d-8c3c-7e1b-8bd2-c27a523562e0" xlink:to="loc_mrna_ArbutusBiopharmaCorporationArbutusAndGenevantSciencesGmbHGenevantMember_019d7591-7882-7230-a91c-755761fcebad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_GlaxoSmithKlineBiologicalsMember_019d759d-8c3c-72ed-a3b1-ba216f5bb398" xlink:href="mrna-20260331.xsd#mrna_GlaxoSmithKlineBiologicalsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019d759d-8c3c-7e1b-8bd2-c27a523562e0" xlink:to="loc_mrna_GlaxoSmithKlineBiologicalsMember_019d759d-8c3c-72ed-a3b1-ba216f5bb398" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019db146-96f3-7b53-8d76-26658aefb63d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019c9a8b-98bf-7d35-a62a-430cf650f499" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019db146-96f3-7b53-8d76-26658aefb63d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019db146-96f3-7b53-8d76-26658aefb63d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019db146-96f3-7b53-8d76-26658aefb63d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019db146-96f3-7b53-8d76-26658aefb63d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019db146-96f3-727a-ac67-0d7de1538227" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019db146-96f3-7b53-8d76-26658aefb63d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019db146-96f3-727a-ac67-0d7de1538227" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntellectualPropertyMember_019db146-b34a-7359-a360-ff7894e85edd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntellectualPropertyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019db146-96f3-727a-ac67-0d7de1538227" xlink:to="loc_us-gaap_IntellectualPropertyMember_019db146-b34a-7359-a360-ff7894e85edd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019db148-4fa1-7a92-9668-0dbf52cc3968" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019c9a8b-98bf-7d35-a62a-430cf650f499" xlink:to="loc_srt_RangeAxis_019db148-4fa1-7a92-9668-0dbf52cc3968" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019db148-4fa1-7a92-9668-0dbf52cc3968_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019db148-4fa1-7a92-9668-0dbf52cc3968" xlink:to="loc_srt_RangeMember_019db148-4fa1-7a92-9668-0dbf52cc3968_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019db148-4fa1-7074-b669-eb2d0a5c1f14" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019db148-4fa1-7a92-9668-0dbf52cc3968" xlink:to="loc_srt_RangeMember_019db148-4fa1-7074-b669-eb2d0a5c1f14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019db148-70d3-7394-b407-f3a8c47930ae" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019db148-4fa1-7074-b669-eb2d0a5c1f14" xlink:to="loc_srt_MaximumMember_019db148-70d3-7394-b407-f3a8c47930ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019db149-0256-7a04-8c50-ab43cae32ed9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-7a15-b65a-caab7f08ad4e" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019db149-0256-7a04-8c50-ab43cae32ed9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019db149-0256-7da7-8fe3-a4aae2c7fde1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-7a15-b65a-caab7f08ad4e" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019db149-0256-7da7-8fe3-a4aae2c7fde1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_019db149-0256-77f8-bb43-8eb7d48f084d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyEstimateOfPossibleLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-7a15-b65a-caab7f08ad4e" xlink:to="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_019db149-0256-77f8-bb43-8eb7d48f084d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019db149-0256-7897-968a-68cb0adb9c7c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-7a15-b65a-caab7f08ad4e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_019db149-0256-7897-968a-68cb0adb9c7c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019db149-0256-7d5a-baf8-a6be546ffd31" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-7a15-b65a-caab7f08ad4e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019db149-0256-7d5a-baf8-a6be546ffd31" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserve_019db149-0256-72b5-9b16-8eb417bf9739" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-7a15-b65a-caab7f08ad4e" xlink:to="loc_us-gaap_LitigationReserve_019db149-0256-72b5-9b16-8eb417bf9739" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNewClaimsFiledNumber_019db149-a19a-7711-9f27-96543dafab2e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNewClaimsFiledNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-7a15-b65a-caab7f08ad4e" xlink:to="loc_us-gaap_LossContingencyNewClaimsFiledNumber_019db149-a19a-7711-9f27-96543dafab2e" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/CommitmentsandContingenciesIndemnificationObligationsDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#CommitmentsandContingenciesIndemnificationObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/CommitmentsandContingenciesIndemnificationObligationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-760f-8ca5-757e0db30c23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019c9a8b-98bf-76b9-bb05-03f0c0a9f972" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-760f-8ca5-757e0db30c23" xlink:to="loc_us-gaap_LossContingenciesTable_019c9a8b-98bf-76b9-bb05-03f0c0a9f972" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_019d7594-1bbf-77ba-b0bc-3e3e9124b474" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019c9a8b-98bf-76b9-bb05-03f0c0a9f972" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_019d7594-1bbf-77ba-b0bc-3e3e9124b474" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_019d7594-1bbf-77ba-b0bc-3e3e9124b474_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_019d7594-1bbf-77ba-b0bc-3e3e9124b474" xlink:to="loc_us-gaap_LossContingencyNatureDomain_019d7594-1bbf-77ba-b0bc-3e3e9124b474_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_019d7594-1bbf-72d5-bdc9-ad8c010ad350" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_019d7594-1bbf-77ba-b0bc-3e3e9124b474" xlink:to="loc_us-gaap_LossContingencyNatureDomain_019d7594-1bbf-72d5-bdc9-ad8c010ad350" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndemnificationGuaranteeMember_019d7594-1bbf-7121-8dd6-2ec850fc5acf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndemnificationGuaranteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_019d7594-1bbf-72d5-bdc9-ad8c010ad350" xlink:to="loc_us-gaap_IndemnificationGuaranteeMember_019d7594-1bbf-7121-8dd6-2ec850fc5acf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyLossInPeriod_019d7594-1bbf-7408-9898-03c444d4a11b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyLossInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-760f-8ca5-757e0db30c23" xlink:to="loc_us-gaap_LossContingencyLossInPeriod_019d7594-1bbf-7408-9898-03c444d4a11b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyPendingClaimsNumber_019d7594-1bbf-73b4-88b3-47dbd01b9f9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyPendingClaimsNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-760f-8ca5-757e0db30c23" xlink:to="loc_us-gaap_LossContingencyPendingClaimsNumber_019d7594-1bbf-73b4-88b3-47dbd01b9f9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019d7594-1bbf-7f5e-9709-f830e36eb3e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019c9a8b-98bf-760f-8ca5-757e0db30c23" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019d7594-1bbf-7f5e-9709-f830e36eb3e5" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/CommitmentsandContingenciesLicensestoPatentedTechnologyDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#CommitmentsandContingenciesLicensestoPatentedTechnologyDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/CommitmentsandContingenciesLicensestoPatentedTechnologyDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-78c3-a26e-d7f205becdaf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_019c9a8b-98bf-79ae-a635-8c7a65e96837" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-78c3-a26e-d7f205becdaf" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_019c9a8b-98bf-79ae-a635-8c7a65e96837" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019c9a8b-98bf-71bf-9d65-d3a15a7d4944" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_019c9a8b-98bf-79ae-a635-8c7a65e96837" xlink:to="loc_srt_CounterpartyNameAxis_019c9a8b-98bf-71bf-9d65-d3a15a7d4944" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-98bf-71bf-9d65-d3a15a7d4944_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019c9a8b-98bf-71bf-9d65-d3a15a7d4944" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-98bf-71bf-9d65-d3a15a7d4944_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-98bf-7f3a-9277-7a126b4993ba" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019c9a8b-98bf-71bf-9d65-d3a15a7d4944" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-98bf-7f3a-9277-7a126b4993ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_NationalInstituteOfAllergyAndInfectiousDiseasesMemberMember_019c9a8b-98bf-7164-b54a-23ebdaf3b190" xlink:href="mrna-20260331.xsd#mrna_NationalInstituteOfAllergyAndInfectiousDiseasesMemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-98bf-7f3a-9277-7a126b4993ba" xlink:to="loc_mrna_NationalInstituteOfAllergyAndInfectiousDiseasesMemberMember_019c9a8b-98bf-7164-b54a-23ebdaf3b190" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_ArbutusBiopharmaCorporationArbutusAndGenevantSciencesGmbHGenevantMember_019d7583-3266-7261-be5c-dd8fdc05586d" xlink:href="mrna-20260331.xsd#mrna_ArbutusBiopharmaCorporationArbutusAndGenevantSciencesGmbHGenevantMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019c9a8b-98bf-7f3a-9277-7a126b4993ba" xlink:to="loc_mrna_ArbutusBiopharmaCorporationArbutusAndGenevantSciencesGmbHGenevantMember_019d7583-3266-7261-be5c-dd8fdc05586d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireIntangibleAssets_019c9a8b-98bf-7f84-be51-5ab51e1fa97f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-78c3-a26e-d7f205becdaf" xlink:to="loc_us-gaap_PaymentsToAcquireIntangibleAssets_019c9a8b-98bf-7f84-be51-5ab51e1fa97f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment_019c9a8b-98bf-7463-a32f-ec4b6db7dc11" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-78c3-a26e-d7f205becdaf" xlink:to="loc_us-gaap_PaymentsToAcquireInProcessResearchAndDevelopment_019c9a8b-98bf-7463-a32f-ec4b6db7dc11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019dcc7e-0992-7233-920d-52e14612d532" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019c9a8b-98bf-78c3-a26e-d7f205becdaf" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019dcc7e-0992-7233-920d-52e14612d532" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/StockBasedCompensationandShareRepurchaseProgramsScheduleofStockBasedCompensationExpenseDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#StockBasedCompensationandShareRepurchaseProgramsScheduleofStockBasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/StockBasedCompensationandShareRepurchaseProgramsScheduleofStockBasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019c9a8b-98bf-7012-8c63-27047b6c9078" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019c9a8b-98bf-76c6-8e2b-02bc2fe6c180" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019c9a8b-98bf-7012-8c63-27047b6c9078" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019c9a8b-98bf-76c6-8e2b-02bc2fe6c180" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019c9a8b-98bf-7ba7-948f-67f1ff066b85" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019c9a8b-98bf-76c6-8e2b-02bc2fe6c180" xlink:to="loc_us-gaap_AwardTypeAxis_019c9a8b-98bf-7ba7-948f-67f1ff066b85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c9a8b-98bf-7ba7-948f-67f1ff066b85_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019c9a8b-98bf-7ba7-948f-67f1ff066b85" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c9a8b-98bf-7ba7-948f-67f1ff066b85_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c9a8b-98bf-774b-91ba-de01d4ea0184" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019c9a8b-98bf-7ba7-948f-67f1ff066b85" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c9a8b-98bf-774b-91ba-de01d4ea0184" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_019c9a8b-98bf-741a-afec-27867257e430" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c9a8b-98bf-774b-91ba-de01d4ea0184" xlink:to="loc_us-gaap_EmployeeStockOptionMember_019c9a8b-98bf-741a-afec-27867257e430" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019c9a8b-98bf-713f-8633-c040604d80ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c9a8b-98bf-774b-91ba-de01d4ea0184" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019c9a8b-98bf-713f-8633-c040604d80ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_PerformanceStockUnitMember_019c9a8b-98bf-7e83-802e-433d6e059a64" xlink:href="mrna-20260331.xsd#mrna_PerformanceStockUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c9a8b-98bf-774b-91ba-de01d4ea0184" xlink:to="loc_mrna_PerformanceStockUnitMember_019c9a8b-98bf-7e83-802e-433d6e059a64" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_019c9a8b-98bf-7f89-97ae-ca1cecb8d8d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019c9a8b-98bf-774b-91ba-de01d4ea0184" xlink:to="loc_us-gaap_EmployeeStockMember_019c9a8b-98bf-7f89-97ae-ca1cecb8d8d9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_019c9a8b-98bf-78a6-8baa-2b7aac9963ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_019c9a8b-98bf-76c6-8e2b-02bc2fe6c180" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_019c9a8b-98bf-78a6-8baa-2b7aac9963ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019c9a8b-98bf-78a6-8baa-2b7aac9963ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019c9a8b-98bf-78a6-8baa-2b7aac9963ce" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019c9a8b-98bf-78a6-8baa-2b7aac9963ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_019c9a8b-98bf-7ff7-b420-bf396df5f62b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_019c9a8b-98bf-78a6-8baa-2b7aac9963ce" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_019c9a8b-98bf-7ff7-b420-bf396df5f62b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_019c9a8b-98bf-7458-923d-4adba9a1c6e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019c9a8b-98bf-7ff7-b420-bf396df5f62b" xlink:to="loc_us-gaap_CostOfSalesMember_019c9a8b-98bf-7458-923d-4adba9a1c6e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_019c9a8b-98bf-7db6-a8c5-4e737d6475ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019c9a8b-98bf-7ff7-b420-bf396df5f62b" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_019c9a8b-98bf-7db6-a8c5-4e737d6475ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_019c9a8b-98bf-757c-8536-9c80f01349ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_019c9a8b-98bf-7ff7-b420-bf396df5f62b" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_019c9a8b-98bf-757c-8536-9c80f01349ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019c9a8b-98bf-7a2f-9023-37f78a0923b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_019c9a8b-98bf-7012-8c63-27047b6c9078" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019c9a8b-98bf-7a2f-9023-37f78a0923b4" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.modernatx.com/role/StockBasedCompensationandShareRepurchaseProgramsNarrativeDetails" xlink:type="simple" xlink:href="mrna-20260331.xsd#StockBasedCompensationandShareRepurchaseProgramsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.modernatx.com/role/StockBasedCompensationandShareRepurchaseProgramsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c9a8b-98bf-711c-9992-a180943679b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c9a8b-98bf-7eec-b6d3-f6b28d75a508" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c9a8b-98bf-711c-9992-a180943679b9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c9a8b-98bf-7eec-b6d3-f6b28d75a508" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis_019d4c58-8f18-7375-8a07-b67ab4396e43" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019c9a8b-98bf-7eec-b6d3-f6b28d75a508" xlink:to="loc_srt_ShareRepurchaseProgramAxis_019d4c58-8f18-7375-8a07-b67ab4396e43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019d4c58-8f18-7375-8a07-b67ab4396e43_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019d4c58-8f18-7375-8a07-b67ab4396e43" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019d4c58-8f18-7375-8a07-b67ab4396e43_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019d4c58-8f18-76c5-be53-20172185e7f9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019d4c58-8f18-7375-8a07-b67ab4396e43" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019d4c58-8f18-76c5-be53-20172185e7f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_mrna_A2022RepurchaseProgramMember_019d4c58-8f18-789d-8db3-9151ceb83460" xlink:href="mrna-20260331.xsd#mrna_A2022RepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_019d4c58-8f18-76c5-be53-20172185e7f9" xlink:to="loc_mrna_A2022RepurchaseProgramMember_019d4c58-8f18-789d-8db3-9151ceb83460" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019d4c57-e0cc-7a47-a714-d61ca8f188ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c9a8b-98bf-711c-9992-a180943679b9" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019d4c57-e0cc-7a47-a714-d61ca8f188ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019d4c57-e0cc-797e-a22a-133c3d05dbba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c9a8b-98bf-711c-9992-a180943679b9" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019d4c57-e0cc-797e-a22a-133c3d05dbba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019d4c58-8f18-7c5c-8108-75f61403b828" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c9a8b-98bf-711c-9992-a180943679b9" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019d4c58-8f18-7c5c-8108-75f61403b828" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_019d4c58-8f18-7256-8c26-4ab1d14c756f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019c9a8b-98bf-711c-9992-a180943679b9" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_019d4c58-8f18-7256-8c26-4ab1d14c756f" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-roles-2025.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization" xlink:type="arc" order="101"/>
  </link:definitionLink>
</link:linkbase>
