<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:ns2="http://www.sec.gov/edgar/common">
    <headerData>
        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001191229</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0001590877</issuerCik>
            <issuerName>REGENXBIO Inc.</issuerName>
            <secFileNumber>001-37553</secFileNumber>
            <issuerAddress>
                <ns2:street1>9804 Medical Center Drive </ns2:street1>
                <ns2:city>Rockville</ns2:city>
                <ns2:stateOrCountry>MD</ns2:stateOrCountry>
                <ns2:zipCode>20850</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>2405528181</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>ARGERIS N KARABELAS</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Director</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC Executive Financial Services</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>8th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>30000</noOfUnitsSold>
            <aggregateMarketValue>351000.00</aggregateMarketValue>
            <noOfUnitsOutstanding>49255966</noOfUnitsOutstanding>
            <approxSaleDate>07/01/2024</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>07/01/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Exercise of Stock Options</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>30000</amountOfSecuritiesAcquired>
            <paymentDate>07/01/2024</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <remarks>The securities to be sold were and will be received upon the exercise of stock options over the next three months.&#13;
The date of acquisition and payment was and will be the date of exercise/sale.&#13;
</remarks>
        <noticeSignature>
            <noticeDate>07/01/2024</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>03/25/2024</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/  Argeris N Karabelas</signature>
        </noticeSignature>
    </formData>
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144
0001191229
XXXXXXXX
LIVE
0001590877
REGENXBIO Inc.
001-37553
9804 Medical Center Drive
Rockville
MD
20850
2405528181
ARGERIS N KARABELAS
Director
COMMON
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
30000
351000.00
49255966
07/01/2024
NASDAQ
Common
07/01/2024
Exercise of Stock Options
Issuer
N
30000
07/01/2024
Cash
Y
The securities to be sold were and will be received upon the exercise of stock options over the next three months.
The date of acquisition and payment was and will be the date of exercise/sale.
07/01/2024
03/25/2024
/s/  Argeris N Karabelas