<?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>0001185998</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
      </filer>
      <liveTestFlag>LIVE</liveTestFlag>



    </filerInfo>
  </headerData>
  <formData>
    <issuerInfo>
      <issuerCik>0000354190</issuerCik>
      <issuerName>Arthur J. Gallagher &amp; Co.</issuerName>
      <secFileNumber>001-09761</secFileNumber>
      <issuerAddress>
        <com:street1>2850 GOLF ROAD</com:street1>
        <com:city>ROLLING MEADOWS</com:city>
        <com:stateOrCountry>IL</com:stateOrCountry>
        <com:zipCode>60008-4050</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>630-773-3800</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>CARY RICHARD C</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>3204</noOfUnitsSold>
      <aggregateMarketValue>697267.46</aggregateMarketValue>
      <noOfUnitsOutstanding>214246000</noOfUnitsOutstanding>
      <approxSaleDate>05/10/2023</approxSaleDate>
      <securitiesExchangeName>NYSE</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>05/10/2023</acquiredDate>
      <natureOfAcquisitionTransaction>Options Granted -03/15/2018</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>983</amountOfSecuritiesAcquired>
      <paymentDate>05/10/2023</paymentDate>
      <natureOfPayment>Cash</natureOfPayment>
    </securitiesToBeSold>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>05/10/2023</acquiredDate>
      <natureOfAcquisitionTransaction>Options Granted - 03/14/2019</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>1000</amountOfSecuritiesAcquired>
      <paymentDate>05/10/2023</paymentDate>
      <natureOfPayment>Cash</natureOfPayment>
    </securitiesToBeSold>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>05/10/2023</acquiredDate>
      <natureOfAcquisitionTransaction>Options Granted -03/12/2020</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>1221</amountOfSecuritiesAcquired>
      <paymentDate>05/10/2023</paymentDate>
      <natureOfPayment>Cash</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <noticeSignature>
      <noticeDate>05/10/2023</noticeDate>
      <signature>/s/Wade Moss, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Richard Cary</signature>
    </noticeSignature>
  </formData>
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144
0001185998
XXXXXXXX
LIVE
0000354190
Arthur J. Gallagher & Co.
001-09761
2850 GOLF ROAD
ROLLING MEADOWS
IL
60008-4050
630-773-3800
CARY RICHARD C
Officer
Common
Fidelity Brokerage Services LLC
900 Salem Street
Smithfield
RI
02917
3204
697267.46
214246000
05/10/2023
NYSE
Common
05/10/2023
Options Granted -03/15/2018
Issuer
N
983
05/10/2023
Cash
Common
05/10/2023
Options Granted - 03/14/2019
Issuer
N
1000
05/10/2023
Cash
Common
05/10/2023
Options Granted -03/12/2020
Issuer
N
1221
05/10/2023
Cash
Y
05/10/2023
/s/Wade Moss, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Richard Cary