6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of January, 2026

Commission File Number 001-34175

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F x      Form 40-F ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1)

Yes ¨      No x

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7)

Yes ¨      No x

Indicate by check mark whether the registrant by furnishing the information contained in this form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes ¨      No x

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82- N/A

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: January 7, 2026

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Renegotiations of Collective Bargaining Agreement

Ecopetrol S.A. (BVC: ECOPETROL; NYSE: EC) (“Ecopetrol” or the “Company”) informs that, in addition to the information published on December 24^th^ 2025 were it was stated that Unión Sindical Obrera (USO) had filled a complaint with the Ministry of Labor of the Collective Bargaining Agreement, the labor organizations Adeco, Sindispetrol, Asopetrogas, Asteco, Trasine, Asintrahc, Sintramen, Sup, and Utipec have started the renegotiation of their respective chapters of the Collective Bargaining Agreement executed with the Company, by filing a complaint with the Ministry of Labor, within the legally-established timeframe.

In accordance with the provisions of the Colombian Labor Code, parties to a collective bargaining agreement may request an amendment to such an agreement by filing a complaint with the Ministry of Labor.

Ecopetrol reaffirms its commitment to open, respectful, and constructive dialogue as a key foundation for reaching agreements that continue to strengthen the well-being of all workers and the country, as well as the joint development of sustainable and valuable solutions.

Bogota D.C., January 7^th^, 2026

Ecopetrol is the largest company in Colombia and one of the mainintegrated energy companies in the American continent, with more than 19,000 employees. In Colombia, it is responsible for more than 60%of the hydrocarbon production of most transportation, logistics, and hydrocarbon refining systems, and it holds leading positions in thepetrochemicals and gas distribution segments. With the acquisition of 51.4% of ISA’s shares, the company participates in energytransmission, the management of real-time systems (XM), and the Barranquilla - Cartagena coastal highway concession. At the internationallevel, Ecopetrol has a stake in strategic basins in the American continent, with Drilling and Exploration operations in the United States(Permian basin and the Gulf of Mexico), Brazil, and Mexico, and, through ISA and its subsidiaries, Ecopetrol holds leading positions inthe power transmission business in Brazil, Chile, Peru, and Bolivia, road concessions in Chile, and the telecommunications sector.

This release contains statements that may be considered forward-lookingstatements within the meaning of Section 27A of the U.S. Securities Act of 1933, as amended, and Section 21E of the U.S. Securities ExchangeAct of 1934, as amended. All forward-looking statements, whether made in this release or in future filings or press releases, or orally,address matters that involve risks and uncertainties, including in respect of the Company’s prospects for growth and its ongoingaccess to capital to fund the Company’s business plan, among others. Consequently, changes in the following factors, among others,could cause actual results to differ materially from those included in the forward-looking statements: market prices of oil & gas,our exploration, and production activities, market conditions, applicable regulations, the exchange rate, the Company’s competitivenessand the performance of Colombia’s economy and industry, to mention a few. We do not intend and do not assume any obligation to updatethese forward-looking statements.

For more information, please contact:

Head of Capital Markets

Diego Nicolas Lopez Reina (a)

Email: investors@ecopetrol.com.co

Head of Corporate Communications (Colombia)

Marcela Ulloa

Email: marcela.ulloa@ecopetrol.com.co