content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001871327</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
      </filerInfo>
    </headerData>
    <formData>
      <issuerInfo>
        <issuerCik>0000062709</issuerCik>
        <issuerName>MARSH &amp; MCLENNAN COMPANIES, INC.</issuerName>
        <secFileNumber>001-05998</secFileNumber>
        <issuerAddress>
          <com:street1>1166 AVENUE OF THE AMERICAS</com:street1>
          <com:city>NEW YORK</com:city>
          <com:stateOrCountry>NY</com:stateOrCountry>
          <com:zipCode>10036</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>2123455000</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Studer Nicholas Mark</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Officer</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>Fidelity Brokerage Services LLC</name>
          <address>
            <com:street1>900 Salem Street</com:street1>
            <com:city>Smithfield</com:city>
            <com:stateOrCountry>RI</com:stateOrCountry>
            <com:zipCode>02917</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>49390</noOfUnitsSold>
        <aggregateMarketValue>11366732.27</aggregateMarketValue>
        <noOfUnitsOutstanding>491131126</noOfUnitsOutstanding>
        <approxSaleDate>03/12/2025</approxSaleDate>
        <securitiesExchangeName>NYSE</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/12/2025</acquiredDate>
        <natureOfAcquisitionTransaction>Option Granted 02/22/2016</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>5667</amountOfSecuritiesAcquired>
        <paymentDate>03/12/2025</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/12/2025</acquiredDate>
        <natureOfAcquisitionTransaction>Option Granted 02/22/2017</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>6490</amountOfSecuritiesAcquired>
        <paymentDate>03/12/2025</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/12/2025</acquiredDate>
        <natureOfAcquisitionTransaction>Option Granted 02/21/2018</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>4070</amountOfSecuritiesAcquired>
        <paymentDate>03/12/2025</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/12/2025</acquiredDate>
        <natureOfAcquisitionTransaction>Option Granted 02/19/2019</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>3049</amountOfSecuritiesAcquired>
        <paymentDate>03/12/2025</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/12/2025</acquiredDate>
        <natureOfAcquisitionTransaction>Option Granted 02/19/2020</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>3881</amountOfSecuritiesAcquired>
        <paymentDate>03/12/2025</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/12/2025</acquiredDate>
        <natureOfAcquisitionTransaction>Option Granted 02/22/2021</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>3163</amountOfSecuritiesAcquired>
        <paymentDate>03/12/2025</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/12/2025</acquiredDate>
        <natureOfAcquisitionTransaction>Option Granted 02/23/2022</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>11739</amountOfSecuritiesAcquired>
        <paymentDate>03/12/2025</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/12/2025</acquiredDate>
        <natureOfAcquisitionTransaction>Option Granted 02/23/2023</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>7587</amountOfSecuritiesAcquired>
        <paymentDate>03/12/2025</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>03/12/2025</acquiredDate>
        <natureOfAcquisitionTransaction>Option Granted 02/22/2024</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>3744</amountOfSecuritiesAcquired>
        <paymentDate>03/12/2025</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Nicholas Studer</name>
          <address>
            <com:street1>1166 Avenue of the Americas</com:street1>
            <com:city>New York,</com:city>
            <com:stateOrCountry>NY</com:stateOrCountry>
            <com:zipCode>10036-2774</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <saleDate>03/03/2025</saleDate>
        <amountOfSecuritiesSold>3649</amountOfSecuritiesSold>
        <grossProceeds>871152.41</grossProceeds>
      </securitiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>03/12/2025</noticeDate>
        <signature>/s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Nicholas Studer</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
metadata_documents: [{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 7703}]
text: 144
  0001871327
  XXXXXXXX
  LIVE
  0000062709
  MARSH & MCLENNAN COMPANIES, INC.
  001-05998
  1166 AVENUE OF THE AMERICAS
  NEW YORK
  NY
  10036
  2123455000
  Studer Nicholas Mark
  Officer
  Common
  Fidelity Brokerage Services LLC
  900 Salem Street
  Smithfield
  RI
  02917
  49390
  11366732.27
  491131126
  03/12/2025
  NYSE
  Common
  03/12/2025
  Option Granted 02/22/2016
  Issuer
  N
  5667
  03/12/2025
  Cash
  Common
  03/12/2025
  Option Granted 02/22/2017
  Issuer
  N
  6490
  03/12/2025
  Cash
  Common
  03/12/2025
  Option Granted 02/21/2018
  Issuer
  N
  4070
  03/12/2025
  Cash
  Common
  03/12/2025
  Option Granted 02/19/2019
  Issuer
  N
  3049
  03/12/2025
  Cash
  Common
  03/12/2025
  Option Granted 02/19/2020
  Issuer
  N
  3881
  03/12/2025
  Cash
  Common
  03/12/2025
  Option Granted 02/22/2021
  Issuer
  N
  3163
  03/12/2025
  Cash
  Common
  03/12/2025
  Option Granted 02/23/2022
  Issuer
  N
  11739
  03/12/2025
  Cash
  Common
  03/12/2025
  Option Granted 02/23/2023
  Issuer
  N
  7587
  03/12/2025
  Cash
  Common
  03/12/2025
  Option Granted 02/22/2024
  Issuer
  N
  3744
  03/12/2025
  Cash
  N
  Nicholas Studer
  1166 Avenue of the Americas
  New York,
  NY
  10036-2774
  Common
  03/03/2025
  3649
  871152.41
  03/12/2025
  /s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Nicholas Studer