Exhibit 5.1

599 Lexington Avenue

New York, NY 10022-6069

+1.212.848.4000

October 1, 2021

Qualtrics International Inc.

333 West River Park Drive

Provo, Utah 84604

Qualtrics International Inc.

Ladies and Gentlemen:

We have acted as counsel to Qualtrics International Inc., a Delaware corporation (the “Company”), in connection with the registration statement on Form S-1 filed by the Company with the Securities and Exchange Commission (the “Commission”) on October 1, 2021 (the “Registration Statement”), relating to the registration under the Securities Act of 1933, as amended (the “Securities Act”), of the resale of shares of the Company’s Class A Common Stock, par value $0.0001 per share (the “Shares”), by certain selling shareholders identified in the Registration Statement. This opinion is being furnished in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act. The offering of the Shares will be as set forth in the prospectus forming part of the Registration Statement (the “Prospectus”).

In that connection, we have reviewed originals or copies of the following documents:

(a)The Registration Statement.

(b)The Prospectus.

(c)The Amended and Restated Certificate of Incorporation of the Company, which is included as Exhibit 3.1 to the Registration Statement.

(d)The Amended and Restated Bylaws of the Company, which are included as Exhibit 3.2 to the Registration Statement.

(e)The originals or copies of such other corporate records of the Company, certificates of public officials and officers of the Company and such other documents and instruments as we have deemed necessary as a basis for the opinions expressed below.

For the purposes of this opinion letter, we have assumed:

(a)The genuineness of all signatures.

(b)The authenticity of the originals of the documents submitted to us.

(c)The conformity to authentic originals of any documents submitted to us as copies.

(d)As to matters of fact, the truthfulness of the representations made in certificates of public officials and officers of the Company.

SHEARMAN.COM

Shearman & Sterling LLP is a limited liability partnership organized in the United States under the laws of the state of Delaware, which laws limit the personal liability of partners.

We have not independently established the validity of the foregoing assumptions.

Based upon the foregoing and upon such other investigation as we have deemed necessary and subject to the qualifications set forth below, we are of the opinion that the Shares have been duly authorized by the Company and are validly issued, fully paid and non-assessable.

Our opinion set forth above is limited to the General Corporation Law of the State of Delaware and we do not express any opinion herein concerning any other law.

This opinion letter is provided solely in connection with the offering of the Shares pursuant to the Registration Statement and is not to be relied upon for any other purpose.

We hereby consent to the filing of this opinion letter as an exhibit to the Registration Statement and to the use of our name therein and in the Prospectus under the caption “Legal Matters.” In giving this consent, we do not hereby admit that we come within the category of persons whose consent is required under Section 7 of the Securities Act, or the rules and regulations of the Commission thereunder.

Very truly yours,

/s/ Shearman & Sterling LLP

RA/rer

KT