<SEC-DOCUMENT>0001127602-22-020415.txt : 20220803
<SEC-HEADER>0001127602-22-020415.hdr.sgml : 20220803
<ACCEPTANCE-DATETIME>20220803174039
ACCESSION NUMBER:		0001127602-22-020415
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20220801
FILED AS OF DATE:		20220803
DATE AS OF CHANGE:		20220803

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Murphy Nicole
		CENTRAL INDEX KEY:			0001910644

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-19311
		FILM NUMBER:		221133861

	MAIL ADDRESS:	
		STREET 1:		BIOGEN INC.
		STREET 2:		225 BINNEY STREET
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142

ISSUER:		

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

	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>
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    <periodOfReport>2022-08-01</periodOfReport>

    <issuer>
        <issuerCik>0000875045</issuerCik>
        <issuerName>BIOGEN INC.</issuerName>
        <issuerTradingSymbol>BIIB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001910644</rptOwnerCik>
            <rptOwnerName>Murphy Nicole</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>225 BINNEY STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CAMBRIDGE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02142</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Head of Pharm Ops and Tech</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

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                <value>Common Stock</value>
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                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
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                <transactionPricePerShare>
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                <sharesOwnedFollowingTransaction>
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            <transactionAmounts>
                <transactionShares>
                    <value>825</value>
                </transactionShares>
                <transactionPricePerShare>
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        </nonDerivativeTransaction>
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    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
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            <conversionOrExercisePrice>
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            </conversionOrExercisePrice>
            <transactionDate>
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            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-08-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>299</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>255</value>
                </sharesOwnedFollowingTransaction>
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            <securityTitle>
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            <transactionDate>
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                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>255</value>
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                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
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                <underlyingSecurityShares>
                    <value>255</value>
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                <value>Restricted Stock Unit</value>
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                <value>2022-08-01</value>
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                <transactionCode>M</transactionCode>
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            <transactionAmounts>
                <transactionShares>
                    <value>825</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
                <footnoteId id="F4"/>
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            <expirationDate>
                <value>2022-08-01</value>
            </expirationDate>
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                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>825</value>
                </underlyingSecurityShares>
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    <footnotes>
        <footnote id="F1">Includes 102.4003 shares acquired under the Biogen Inc. employee stock purchase plan.</footnote>
        <footnote id="F2">This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.</footnote>
        <footnote id="F3">This award was granted to the reporting person on August 1, 2019. The number of RSUs reported represents the maximum possible number of shares that are eligible for vesting,
which is 200% of the number of shares at target payout. One-third of these RSUs are eligible to vest on each of the first three anniversaries of the grant date. The actual number of
shares that will vest on each vesting date will be determined by comparing the price of Biogen common stock on such vesting date to the price on the grant date (i.e., number of
vested shares = number of shares at target payout times (the 30-day average closing stock price ending on the vesting date divided by the 30-day average closing stock price
following and including the grant date)).</footnote>
        <footnote id="F4">This award was granted to the reporting person on August 1, 2019 and vested in full on August 1, 2022.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Wendell Taylor, attorney in fact for Nicole Murphy</signatureName>
        <signatureDate>2022-08-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
