    <SEC-DOCUMENT>0001193125-25-097749-index.html : 20250428
    <SEC-HEADER>0001193125-25-097749.hdr.sgml : 20250428
    <ACCEPTANCE-DATETIME>20250425214028
    ACCESSION NUMBER:		0001193125-25-097749
    CONFORMED SUBMISSION TYPE:	DEFA14A
    PUBLIC DOCUMENT COUNT:		3
    FILED AS OF DATE:		20250428
    DATE AS OF CHANGE:		20250425

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			BIOGEN INC.
    		CENTRAL INDEX KEY:			0000875045
    		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
    		ORGANIZATION NAME:           	03 Life Sciences
    		EIN:				330112644
    		STATE OF INCORPORATION:			DE
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		DEFA14A
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	000-19311
    		FILM NUMBER:		25875785

    	BUSINESS ADDRESS:
    		STREET 1:		225 BINNEY STREET
    		CITY:			CAMBRIDGE
    		STATE:			MA
    		ZIP:			02142
    		BUSINESS PHONE:		7814642000

    	MAIL ADDRESS:
    		STREET 1:		225 BINNEY STREET
    		CITY:			CAMBRIDGE
    		STATE:			MA
    		ZIP:			02142

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	BIOGEN IDEC INC.
    		DATE OF NAME CHANGE:	20070427

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	BIOGEN IDEC INC
    		DATE OF NAME CHANGE:	20031112

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	IDEC PHARMACEUTICALS CORP / DE
    		DATE OF NAME CHANGE:	19970530
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>DEFA14A
    <SEQUENCE>1
    <FILENAME>d916837ddefa14a.htm
    <DESCRIPTION>DEFA14A
    <TEXT>
    Document 1 - file: d916837ddefa14a.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>2
    <FILENAME>g916837dsp028.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 2 - file: g916837dsp028.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>3
    <FILENAME>g916837dsp029.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 3 - file: g916837dsp029.jpg

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    </SEC-DOCUMENT>