GARTNER INC

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Check the appropriate box:

GARTNER, INC.

(Name of Registrant as Specified in Its Charter)

Payment of Filing Fee (Check all boxes that apply):

Dear Stockholder:

On behalf of the Board of Directors and Management of Gartner, Inc., you are invited to attend our 2024 Annual Meeting of Stockholders to be held on Thursday, June 6, 2024, at 10 a.m. Eastern Time, via live audio webcast over the internet atwww.virtualshareholdermeeting.com/IT2024. Stockholders or their legal proxy holders can participate, submit questions, vote, and examine our stockholder list at the Annual Meeting by visitingwww.virtualshareholdermeeting.com/IT2024 and using a valid control number. As always, we encourage you to vote your shares prior to the Annual Meeting.

Details of the business to be conducted at the meeting are given in the Notice of Annual Meeting of Stockholders and Proxy Statement which follow this letter. The 2023 Annual Report to Stockholders is also included with these materials.

We have mailed to many of our stockholders a Notice of Internet Availability of Proxy Materials (the “Notice”) containing instructions on how to access our 2024 Proxy Statement and our 2023 Annual Report to Stockholders, and how to vote online on the three management Proposals, put before you this year. The Notice also includes instructions on how to request a paper or email copy of the proxy materials, including the Notice of Annual Meeting, Proxy Statement and Annual Report, and proxy card or voting instruction card. Stockholders who previously either requested paper copies of the proxy materials or elected to receive the proxy materials electronically did not receive a Notice and will receive the proxy materials in the format requested.

In addition, by following the e-consent instructions in the proxy card, stockholders may go paperless in future solicitations and request proxy materials electronically by email on an ongoing basis.

Your vote is important. Whether or not you plan to attend the Annual Meeting, we urge you to review the proxy materials and vote your shares, regardless of the number of shares you hold, as soon as possible. You may vote by proxy over the internet or by telephone using the instructions provided in the Notice. Alternatively, if you received paper copies of the proxy materials by mail, you can also vote by following the instructions on the proxy card or voting instruction card. Instructions regarding the three methods of voting are contained in the Notice, proxy card or voting instruction card.

If you have any questions about the meeting, please contact our Investor Relations Department at investor.relations@gartner.com.

Sincerely,

Eugene A. Hall

Chief Executive Officer

2024 Proxy Statement

56 Top Gallant Road

Stamford, Connecticut 06902

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To be admitted to the Annual Meeting, please visitwww.virtualshareholdermeeting.com/IT2024. Online check-in will be available approximately 15 minutes before the meeting starts. Stockholders of record as of the close of business on April 8, 2024, the Record Date, are entitled to participate in and vote at the Annual Meeting. To participate in the Annual Meeting, including to vote, ask questions, and view the list of registered stockholders as of the Record Date during the Annual Meeting, stockholders of record should go to the meeting website atwww.virtualshareholdermeeting.com/IT2024, enter the 16-digit control number found on your proxy card or Notice of Internet Availability of Proxy Materials (the “Notice”), and follow the instructions on the website. If your shares are held in street name and your voting instruction form or Notice indicates that you may vote those shares through the http://www.proxyvote.com website, then you may access, participate in, and vote at the annual meeting with the 16-digit access code indicated on that voting instruction form or Notice. Otherwise, stockholders who hold their shares in street name should contact their bank, broker or other nominee (preferably at least 5 days before the Annual Meeting) and obtain a “legal proxy” in order to be able to attend, participate in or vote at the Annual Meeting. For more information about how to attend the Annual Meeting online, please see “Information Concerning Proxy Materials and the Voting of Proxies –How Can I Participate in the 2024 Annual Stockholders’ Meeting?” on page 58 of the Proxy Statement.

In the event of a technical malfunction or other situation that the meeting chair determines may affect the ability of the meeting to satisfy the requirements for a meeting of stockholders to be held by means of remote communication under the Delaware General Corporation Law, or that otherwise makes it advisable to adjourn the meeting, the chair of the meeting will convene the meeting at 10:30 a.m. Eastern Time on the date specified above and at the location specified above solely for the purpose of adjourning the meeting to reconvene at a date, time and physical or virtual location announced by the meeting chair. Under either of the foregoing circumstances, we will post information regarding the announcement on the investors page of the company’s website athttps://investor.gartner.com.

Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting of Stockholders to Be Held on June 6, 2024: We are making this Notice of Annual Meeting, this Proxy Statement and our 2023 Annual Report available on the Internet atwww.proxyvote.com and mailing copies of these Proxy Materials to certain stockholders on or about April 16, 2024.

By Order of the Board of Directors,

Thomas Kim

Executive Vice President, General Counsel & Secretary

Stamford, Connecticut

2024 Proxy Statement

TABLE OF CONTENTS

2024 Proxy Statement