ViewRay (VRAYQ) 8-K Entry into a Material Definitive Agreement

Exhibit 5.1

December 6, 2019

ViewRay, Inc.

47,782,500 Shares of Common Stock

Ladies and Gentlemen:

We have acted as counsel for ViewRay, Inc., a Delaware corporation (the “Company”), in connection with the preparation and filing with the Securities and Exchange Commission (the “Commission”) of the Prospectus Supplement, dated December 3, 2019 (the “Prospectus Supplement”), of the Company, filed with the Commission and relating to the issuance and sale by the Company of an aggregate of 47,782,500 shares (the “Shares”) of Common Stock, par value $0.01 per share (the “Common Stock”), of the Company.

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, as amended; (b) theBy-laws of the Company; (c) resolutions adopted by the Board of Directors of the Company on November 15, 2019, and by the Financing Committee of the Board of Directors on December 3, 2019; and (d) the Registration Statement onForm S-3 (RegistrationNo. 333-229145) filed with the Commission on January 7, 2019 (the “Registration Statement”), with respect to registration under the Securities Act of 1933, as amended (the “Act”), of $250,000,000 aggregate amount of various securities of the Company, to be issued from time to time by the Company. As to various questions of fact material to this opinion, we have relied upon representations of officers or directors of the Company and documents furnished to us by the Company without independent verification of their accuracy.

In rendering this opinion, 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 due authorization, execution and delivery of the agreements by all parties thereto (other than the Company), 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.

Based on the foregoing and subject to the qualifications set forth herein, we are of opinion that the Shares, when issued and delivered to and paid for by the Underwriters pursuant to the Underwriting Agreement, 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 laws of the State of New York, the General Corporation Law of the State of Delaware.

We are aware that we are referred to under the heading “Legal Matters” in the Prospectus Supplement. We hereby consent to such use of our name therein and to the filing of this opinion as Exhibit 5.1 to the Company’s Current Report on Form8-K filed on December 6, 2019, and to the incorporation by reference of this opinion into 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 Act or the rules and regulations of the Commission promulgated thereunder.

Very truly yours,

/s/ Cravath, Swaine & Moore LLP

ViewRay, Inc.

2 Thermo Fisher Way

Oakwood Village, OH 44146

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