<?xml version="1.0" encoding="UTF-8"?><ns2:edgarSubmission xmlns:com="http://www.sec.gov/edgar/common" xmlns:ns2="http://www.sec.gov/edgar/ownership">
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        <ns2:filerInfo>
            <ns2:filer>
                <ns2:filerCredentials>
                    <ns2:cik>0001410235</ns2:cik>
                    <ns2:ccc>XXXXXXXX</ns2:ccc>
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            </ns2:filer>
            <ns2:liveTestFlag>LIVE</ns2:liveTestFlag>



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    <ns2:formData>
        <ns2:issuerInfo>
            <ns2:issuerCik>0000354190</ns2:issuerCik>
            <ns2:issuerName>Arthur J. Gallagher &amp; Co.</ns2:issuerName>
            <ns2:secFileNumber>001-09761</ns2:secFileNumber>
            <ns2:issuerAddress>
                <com:street1>2850 Golf Road</com:street1>
                <com:city>Rolling Meadows</com:city>
                <com:stateOrCountry>IL</com:stateOrCountry>
                <com:zipCode>60008</com:zipCode>
            </ns2:issuerAddress>
            <ns2:issuerContactPhone>1-630-773-3800</ns2:issuerContactPhone>
            <ns2:nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Walter D. Bay</ns2:nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <ns2:relationshipsToIssuer>
                <ns2:relationshipToIssuer>Officer</ns2:relationshipToIssuer>
            </ns2:relationshipsToIssuer>
        </ns2:issuerInfo>
        <ns2:securitiesInformation>
            <ns2:securitiesClassTitle>Common Stock</ns2:securitiesClassTitle>
            <ns2:brokerOrMarketmakerDetails>
                <ns2:name>Goldman Sachs &amp; Co. LLC</ns2:name>
                <ns2:address>
                    <com:street1>200 West Street</com:street1>
                    <com:city>New York</com:city>
                    <com:stateOrCountry>NY</com:stateOrCountry>
                    <com:zipCode>10282</com:zipCode>
                </ns2:address>
            </ns2:brokerOrMarketmakerDetails>
            <ns2:noOfUnitsSold>6335</ns2:noOfUnitsSold>
            <ns2:aggregateMarketValue>1796479.3</ns2:aggregateMarketValue>
            <ns2:noOfUnitsOutstanding>218500000</ns2:noOfUnitsOutstanding>
            <ns2:approxSaleDate>07/30/2024</ns2:approxSaleDate>
            <ns2:securitiesExchangeName>NYSE</ns2:securitiesExchangeName>
        </ns2:securitiesInformation>
        <ns2:securitiesToBeSold>
            <ns2:securitiesClassTitle>Common Stock</ns2:securitiesClassTitle>
            <ns2:acquiredDate>03/14/2022</ns2:acquiredDate>
            <ns2:natureOfAcquisitionTransaction>Acquired as compensation -- Restricted Stock Units</ns2:natureOfAcquisitionTransaction>
            <ns2:nameOfPersonfromWhomAcquired>Issuer</ns2:nameOfPersonfromWhomAcquired>
            <ns2:isGiftTransaction>N</ns2:isGiftTransaction>
            <ns2:amountOfSecuritiesAcquired>5631</ns2:amountOfSecuritiesAcquired>
            <ns2:paymentDate>03/14/2022</ns2:paymentDate>
            <ns2:natureOfPayment>Compensation</ns2:natureOfPayment>
        </ns2:securitiesToBeSold>
        <ns2:securitiesToBeSold>
            <ns2:securitiesClassTitle>Common Stock</ns2:securitiesClassTitle>
            <ns2:acquiredDate>03/16/2022</ns2:acquiredDate>
            <ns2:natureOfAcquisitionTransaction>Acquired as compensation -- Restricted Stock Units</ns2:natureOfAcquisitionTransaction>
            <ns2:nameOfPersonfromWhomAcquired>Issuer</ns2:nameOfPersonfromWhomAcquired>
            <ns2:isGiftTransaction>N</ns2:isGiftTransaction>
            <ns2:amountOfSecuritiesAcquired>510</ns2:amountOfSecuritiesAcquired>
            <ns2:paymentDate>03/16/2022</ns2:paymentDate>
            <ns2:natureOfPayment>Compensation</ns2:natureOfPayment>
        </ns2:securitiesToBeSold>
        <ns2:securitiesToBeSold>
            <ns2:securitiesClassTitle>Common Stock</ns2:securitiesClassTitle>
            <ns2:acquiredDate>03/15/2022</ns2:acquiredDate>
            <ns2:natureOfAcquisitionTransaction>Acquired as compensation -- Restricted Stock Units</ns2:natureOfAcquisitionTransaction>
            <ns2:nameOfPersonfromWhomAcquired>Issuer</ns2:nameOfPersonfromWhomAcquired>
            <ns2:isGiftTransaction>N</ns2:isGiftTransaction>
            <ns2:amountOfSecuritiesAcquired>194</ns2:amountOfSecuritiesAcquired>
            <ns2:paymentDate>03/15/2022</ns2:paymentDate>
            <ns2:natureOfPayment>Compensation</ns2:natureOfPayment>
        </ns2:securitiesToBeSold>
        <ns2:nothingToReportFlagOnSecuritiesSoldInPast3Months>N</ns2:nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <ns2:securitiesSoldInPast3Months>
            <ns2:sellerDetails>
                <ns2:name>Walter D. Bay</ns2:name>
                <ns2:address>
                    <com:street1>2850 Golf Road</com:street1>
                    <com:city>Rolling Meadows</com:city>
                    <com:stateOrCountry>IL</com:stateOrCountry>
                    <com:zipCode>60008</com:zipCode>
                </ns2:address>
            </ns2:sellerDetails>
            <ns2:securitiesClassTitle>Common Stock</ns2:securitiesClassTitle>
            <ns2:saleDate>06/20/2024</ns2:saleDate>
            <ns2:amountOfSecuritiesSold>8303</ns2:amountOfSecuritiesSold>
            <ns2:grossProceeds>2181237.92</ns2:grossProceeds>
        </ns2:securitiesSoldInPast3Months>
        <ns2:noticeSignature>
            <ns2:noticeDate>07/30/2024</ns2:noticeDate>
            <ns2:planAdoptionDates/>
            <ns2:signature>Goldman Sachs &amp; Co. LLC on behalf of Walter D. Bay</ns2:signature>
        </ns2:noticeSignature>
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144
0001410235
XXXXXXXX
LIVE
0000354190
Arthur J. Gallagher & Co.
001-09761
2850 Golf Road
Rolling Meadows
IL
60008
1-630-773-3800
Walter D. Bay
Officer
Common Stock
Goldman Sachs & Co. LLC
200 West Street
New York
NY
10282
6335
1796479.3
218500000
07/30/2024
NYSE
Common Stock
03/14/2022
Acquired as compensation -- Restricted Stock Units
Issuer
N
5631
03/14/2022
Compensation
Common Stock
03/16/2022
Acquired as compensation -- Restricted Stock Units
Issuer
N
510
03/16/2022
Compensation
Common Stock
03/15/2022
Acquired as compensation -- Restricted Stock Units
Issuer
N
194
03/15/2022
Compensation
N
Walter D. Bay
2850 Golf Road
Rolling Meadows
IL
60008
Common Stock
06/20/2024
8303
2181237.92
07/30/2024
Goldman Sachs & Co. LLC on behalf of Walter D. Bay