ClearSign Technologies Corp

SCHEDULE 14A

(RULE 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

Filed by the Registrant ⌧

Filed by a Party other than the Registrant¨

Check the appropriate box:

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

Payment of Filing Fee (Check the appropriate box):

8023 East 63rd** Place, Suite 101**

Tulsa, Oklahoma 74133

Dear Stockholder:

You are invited to attend the 2026 annual meeting of stockholders (the “Annual Meeting”) of ClearSign Technologies Corporation (the “Company,” “we,” “us” or “our”) on June 8, 2026 at 1:00 p.m. Central Time. The Annual Meeting will be a completely virtual meeting conducted live via the Internet. You will be able to attend the Annual Meeting online and submit your questions during the Annual Meeting by visiting www.virtualshareholdermeeting.com/CLIR2026.

At this year’s meeting, you will be asked to vote on: (1) the election of four members of our board of directors to serve until the next annual meeting of stockholders or until their respective successors have been elected and qualified; (2) the approval, on an advisory basis, of the appointment of BPM CPA LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2026; (3) the approval of the amended and restated ClearSign Technologies Corporation 2021 Equity Incentive Plan (the “A&R 2021 Plan”), as more fully described in the accompanying proxy statement; (4) the approval, on an advisory basis, of the compensation paid to our named executive officers; and (5) the approval of one or more adjournments of the Annual Meeting to a later date or dates to solicit additional proxies if there are insufficient votes to approve the A&R 2021 Plan or in the absence of a quorum.

Our board of directors (the “Board”) has fixed the close of business on April 13, 2026 as the record date for determining the stockholders entitled to notice of and to vote at the Annual Meeting and any adjournment and postponements thereof (the “Record Date”).

Please use this opportunity to take part in the affairs of the Company by voting on the business to come before this meeting. If you are a record holder of the Company’s common stock on the Record Date, you are eligible to vote with respect to these matters either electronically, at the meeting, or by proxy. It is important that your shares be voted, whether or not you plan to attend the meeting, to ensure the presence of a quorum. We urge you to authorize your proxy in advance by following the instructions printed on your proxy card. Returning the proxy card does not deprive you of your right to attend the virtual meeting and vote your shares.

Sincerely,

/s/ Colin James Deller

Colin James Deller, Chief Executive Officer

Tulsa, Oklahoma

April 28, 2026

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE STOCKHOLDER MEETING TO BE HELD ON JUNE 8, 2026; THIS PROXY STATEMENT AND THE 2025 ANNUAL REPORT ON FORM 10-K ARE AVAILABLE AT WWW.PROXYVOTE.COM

8023 East 63rd** Place Suite 101**

Tulsa, Oklahoma 74133

Notice of 2026 Annual Meeting of Stockholders

to be held June 8, 2026

To the Stockholders of ClearSign Technologies Corporation:

The 2026 annual meeting of stockholders (the “Annual Meeting”) will be held at 1:00 p.m. Central Time on June 8, 2026. The Annual Meeting will be a virtual meeting of stockholders conducted live via the Internet. You will be able to attend the Annual Meeting online by visiting www.virtualshareholdermeeting.com/CLIR2026. During the Annual Meeting, stockholders will be asked to vote either directly or by proxy on the following matters discussed herein:

(3)the approval of the amended and restated ClearSign Technologies Corporation 2021 Equity Incentive Plan, as more fully described in the accompanying proxy statement (the “A&R 2021 Plan”);

(5) the approval of one or more adjournments of the Annual Meeting to a later date or dates to solicit additional proxies if there are insufficient votes to approve the A&R 2021 Plan or in the absence of a quorum.

If you are a stockholder of record as of April 13, 2026, you may vote at the Annual Meeting as further described in the accompanying proxy statement. The Notice of Internet Availability of Proxy Materials (“Notice of Internet Availability”), proxy statement and form of proxy are being distributed and made available on the Internet on or about April 28, 2026.

Dated: April 28, 2026

By Order of the Board of Directors

/s/ Brent Hinds

Brent Hinds

Chief Financial Officer and Secretary​

Whether or not you expect to attend the Annual Meeting, please vote at your earliest convenience by following the instructions in the Notice of Internet Availability or the proxy card you received in the mail.