<SEC-DOCUMENT>0001562180-25-006078.txt : 20250903
<SEC-HEADER>0001562180-25-006078.hdr.sgml : 20250903
<ACCEPTANCE-DATETIME>20250903164746
ACCESSION NUMBER:		0001562180-25-006078
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250901
FILED AS OF DATE:		20250903
DATE AS OF CHANGE:		20250903

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Chan Mitchell
		CENTRAL INDEX KEY:			0001789335
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-37553
		FILM NUMBER:		251290523

	MAIL ADDRESS:	
		STREET 1:		C/O VIELA BIO, INC., ONE MEDIMMUNE WAY
		STREET 2:		FIRST FLOOR, AREA TWO
		CITY:			GAITHERSBURG
		STATE:			MD
		ZIP:			20878

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			REGENXBIO Inc.
		CENTRAL INDEX KEY:			0001590877
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		ORGANIZATION NAME:           	03 Life Sciences
		EIN:				471851754
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		9804 MEDICAL CENTER DRIVE
		CITY:			ROCKVILLE
		STATE:			MD
		ZIP:			20850
		BUSINESS PHONE:		240-552-8181

	MAIL ADDRESS:	
		STREET 1:		9804 MEDICAL CENTER DRIVE
		CITY:			ROCKVILLE
		STATE:			MD
		ZIP:			20850

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	REGENXBIO, Inc.
		DATE OF NAME CHANGE:	20150116

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ReGenX Biosciences, LLC
		DATE OF NAME CHANGE:	20131101
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primarydocument.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-09-01</periodOfReport>

    <notSubjectToSection16>false</notSubjectToSection16>

    <issuer>
        <issuerCik>0001590877</issuerCik>
        <issuerName>REGENXBIO Inc.</issuerName>
        <issuerTradingSymbol>RGNX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001789335</rptOwnerCik>
            <rptOwnerName>Chan Mitchell</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O REGENXBIO INC.</rptOwnerStreet1>
            <rptOwnerStreet2>9804 MEDICAL CENTER DRIVE</rptOwnerStreet2>
            <rptOwnerCity>ROCKVILLE</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20850</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>false</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>Chief Financial Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-09-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4901.00</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.93</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>53968.00</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares of common stock withheld to pay taxes upon the vesting of restricted stock units originally granted to the reporting person on September 16, 2024. The number of shares withheld was determined based on the closing price of the issuer's common stock on August 29, 2025.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Patrick J. Christmas as attorney-in-fact</signatureName>
        <signatureDate>2025-09-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
