Exhibit 5.1

		WORLDWIDE PLAZA
JOHN W. WHITE EVAN R. CHESLER STEPHEN L. GORDON ROBERT H. BARON DAVID MERCADO CHRISTINE A. VARNEY PETER T. BARBUR MICHAEL S. GOLDMAN RICHARD HALL JULIE A. NORTH ANDREW W. NEEDHAM STEPHEN L. BURNS KATHERINE B. FORREST KEITH R. HUMMEL DAVID J. KAPPOS DANIEL SLIFKIN ROBERT I. TOWNSEND, III PHILIP J. BOECKMAN WILLIAM V. FOGG FAIZA J. SAEED RICHARD J. STARK THOMAS E. DUNN MARK I. GREENE DAVID R. MARRIOTT MICHAEL A. PASKIN ANDREW J. PITTS MICHAEL T. REYNOLDS	ANTONY L. RYAN GEORGE E. ZOBITZ GEORGE A. STEPHANAKIS DARIN P. MCATEE GARY A. BORNSTEIN TIMOTHY G. CAMERON KARIN A. DEMASI DAVID S. FINKELSTEIN RACHEL G. SKAISTIS PAUL H. ZUMBRO ERIC W. HILFERS GEORGE F. SCHOEN ERIK R. TAVZEL CRAIG F. ARCELLA DAMIEN R. ZOUBEK LAUREN ANGELILLI TATIANA LAPUSHCHIK ALYSSA K. CAPLES JENNIFER S. CONWAY MINH VAN NGO KEVIN J. ORSINI MATTHEW MORREALE JOHN D. BURETTA J. WESLEY EARNHARDT YONATAN EVEN BENJAMIN GRUENSTEIN JOSEPH D. ZAVAGLIA	825 EIGHTH AVENUE NEW YORK, NY 10019 - 7475 TELEPHONE: + 1 - 212 - 474 - 1000 FACSIMILE: + 1 - 212  - 474 - 3700 CITYPOINT ONE ROPEMAKER STREET LONDON EC2Y 9HR TELEPHONE: + 44 - 20  - 7453 - 1000 FACSIMILE: + 44 - 20 - 7860 - 1150	STEPHEN M. KESSING LAUREN A. MOSKOWITZ DAVID J. PERKINS JOHNNY G. SKUMPIJA J. LEONARD TETI, II D. SCOTT BENNETT TING S. CHEN CHRISTOPHER K. FARGO KENNETH C. HALCOM DAVID M. STUART AARON M. GRUBER O. KEITH HALLAM, III OMID H. NASAB DAMARIS HERNÁNDEZ JONATHAN J. KATZ RORY A. LERARIS KARA L. MUNGOVAN MARGARET T. SEGALL NICHOLAS A. DORSEY ANDREW C. ELKEN JENNY HOCHENBERG VANESSA A. LAVELY G.J. LIGELIS JR. MICHAEL E. MARIANI LAUREN R. KENNEDY SASHA ROSENTHAL-LARREA ALLISON M. WEIN	MICHAEL P. ADDIS JUSTIN C. CLARKE SHARONMOYEE GOSWAMI C. DANIEL HAAREN EVAN MEHRAN NORRIS LAUREN M. ROSENBERG MICHAEL L. ARNOLD HEATHER A. BENJAMIN MATTHEW J. BOBBY DANIEL J. CERQUEIRA ALEXANDRA C. DENNING HELAM GEBREMARIAM MATTHEW G. JONES MATTHEW M. KELLY DAVID H. KORN BRITTANY L. SUKIENNIK ANDREW M. WARK PARTNER EMERITUS SAMUEL C. BUTLER OF COUNSEL MICHAEL L. SCHLER CHRISTOPHER J. KELLY

February 5, 2021

Illumina, Inc.

Registration Statement on Form S-4

Ladies and Gentlemen:

We have acted as counsel to Illumina, Inc., a Delaware corporation (the “Company”), in connection with the offer and sale by the Company of up to 15,254,237 shares of common stock (the “Shares”), par value $0.01 per share, of the Company, to be issued pursuant to the Agreement and Plan of Merger, dated as of September 20, 2020 (as amended on February 4, 2021, the “Merger Agreement”), by and among the Company, SDG Ops, Inc., a wholly owned subsidiary of the Company, SDG Ops, LLC, a wholly owned subsidiary of the Company, and GRAIL, Inc., a Delaware corporation (“GRAIL”).

In that connection, we have examined originals, or copies certified or otherwise identified to our satisfaction, of such documents, corporate records and other instruments as we have deemed necessary or appropriate for the purposes of this opinion, including: (a) the Amended and Restated Certificate of Incorporation of the Company, certified by the Secretary of State of the State of Delaware as of February 4, 2021, (b) the Amended and Restated Bylaws of the Company, as adopted on June 6, 2019, (c) the resolutions adopted by the Board of Directors of the Company on September 14, 2020, (d) the registration statement on Form S-4 (Registration No. 333-250941) filed with the Securities and Exchange Commission (the “Commission”) on November 25, 2020 with respect to the registration of the Shares under the Securities Act of 1933, as amended (the “Securities Act”), as amended by Amendment No. 1 thereto filed with the Commission on February 5, 2021 (such registration statement, as amended, the “Registration Statement”), and (e) the Merger Agreement.

In expressing the opinions set forth herein, we have assumed, with your consent and without independent investigation or verification, the genuineness of all signatures, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals and the conformity to authentic original documents of all documents submitted to us as duplicates or copies. We have relied, with respect to certain factual matters, on statements of public officials and officers and other representatives of the Company.

Based on the foregoing and subject to the qualifications and assumptions set forth herein, we are of opinion that the Shares, upon issuance and delivery thereof to former holders of GRAIL’s (a) Class A Common Stock, par value $0.001 per share, (b) Class B Common Stock, par value $0.001 per share, (c) Series A Preferred Stock, par value $0.001 per share, (d) Series B Preferred Stock, par value $0.001 per share, (e) Series C Preferred Stock, par value $0.001 per share, (f) Series D Preferred Stock, par value $0.001 per share, and (g) Company Equity Awards (as defined in the Merger Agreement) pursuant to the terms of the Merger Agreement and in the manner contemplated by the Registration Statement, will be validly issued, fully paid and nonassessable.

We are admitted to practice in the State of New York, and we express no opinion as to matters governed by any laws other than the General Corporation Law of the State of Delaware.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement. We also consent to the reference to our firm under the caption “Validity of Illumina Common Stock and CVRs” in the consent solicitation statement/prospectus constituting a part of the Registration Statement. In giving this consent, we do not hereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Very truly yours,

/s/    Cravath, Swaine & Moore LLP

Illumina, Inc.

5200 Illumina Way

San Diego, CA 92122

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