    <SEC-DOCUMENT>0001558370-25-005268-index.html : 20250423
    <SEC-HEADER>0001558370-25-005268.hdr.sgml : 20250423
    <ACCEPTANCE-DATETIME>20250423161708
    ACCESSION NUMBER:		0001558370-25-005268
    CONFORMED SUBMISSION TYPE:	ARS
    PUBLIC DOCUMENT COUNT:		1
    CONFORMED PERIOD OF REPORT:	20241231
    FILED AS OF DATE:		20250423
    DATE AS OF CHANGE:		20250423
    EFFECTIVENESS DATE:		20250423

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			Generation Bio Co.
    		CENTRAL INDEX KEY:			0001733294
    		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
    		ORGANIZATION NAME:           	03 Life Sciences
    		EIN:				814301281
    		STATE OF INCORPORATION:			DE
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		ARS
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-39319
    		FILM NUMBER:		25861718

    	BUSINESS ADDRESS:
    		STREET 1:		301 BINNEY STREET
    		CITY:			CAMBRIDGE
    		STATE:			MA
    		ZIP:			02142
    		BUSINESS PHONE:		857-529-5908

    	MAIL ADDRESS:
    		STREET 1:		301 BINNEY STREET
    		CITY:			CAMBRIDGE
    		STATE:			MA
    		ZIP:			02142
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>ARS
    <SEQUENCE>1
    <FILENAME>gbio-20241231xars.pdf
    <DESCRIPTION>ARS
    <TEXT>
    Document 1 - file: gbio-20241231xars.pdf

    </DOCUMENT>
    </SEC-DOCUMENT>