<?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>0001652824</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>KENNETH MILLS</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Director</relationshipToIssuer>
                <relationshipToIssuer>Officer</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>45000</noOfUnitsSold>
            <aggregateMarketValue>708300.00</aggregateMarketValue>
            <noOfUnitsOutstanding>49255966</noOfUnitsOutstanding>
            <approxSaleDate>05/14/2024</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>05/14/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Exercise of Stock Options</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>45000</amountOfSecuritiesAcquired>
            <paymentDate>05/14/2024</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>10b5-1 Sales for KENNETH THOMAS MILLS</name>
                <address>
                    <ns2:street1>9804 Medical Center Drive </ns2:street1>
                    <ns2:city>Rockville</ns2:city>
                    <ns2:stateOrCountry>MD</ns2:stateOrCountry>
                    <ns2:zipCode>20850</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>04/15/2024</saleDate>
            <amountOfSecuritiesSold>15000</amountOfSecuritiesSold>
            <grossProceeds>272871.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>10b5-1 Sales for KENNETH THOMAS MILLS</name>
                <address>
                    <ns2:street1>9804 Medical Center Drive </ns2:street1>
                    <ns2:city>Rockville</ns2:city>
                    <ns2:stateOrCountry>MD</ns2:stateOrCountry>
                    <ns2:zipCode>20850</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>03/14/2024</saleDate>
            <amountOfSecuritiesSold>15000</amountOfSecuritiesSold>
            <grossProceeds>327942.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <remarks>The securities to be sold were and will be received upon the exercise of stock options over the next three months. The dates of acquisition and payment were and will be the dates of exercise/sale.</remarks>
        <noticeSignature>
            <noticeDate>05/14/2024</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>09/19/2023</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Kenneth Mills</signature>
        </noticeSignature>
    </formData>
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144
0001652824
XXXXXXXX
LIVE
0001590877
REGENXBIO Inc.
001-37553
9804 Medical Center Drive
Rockville
MD
20850
2405528181
KENNETH MILLS
Director
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
45000
708300.00
49255966
05/14/2024
NASDAQ
Common
05/14/2024
Exercise of Stock Options
Issuer
N
45000
05/14/2024
Cash
N
10b5-1 Sales for KENNETH THOMAS MILLS
9804 Medical Center Drive
Rockville
MD
20850
Common
04/15/2024
15000
272871.00
10b5-1 Sales for KENNETH THOMAS MILLS
9804 Medical Center Drive
Rockville
MD
20850
Common
03/14/2024
15000
327942.00
The securities to be sold were and will be received upon the exercise of stock options over the next three months. The dates of acquisition and payment were and will be the dates of exercise/sale.
05/14/2024
09/19/2023
/s/ Kenneth Mills