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 July, 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: July 20, 2026

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Ecopetrol Resumes the Tender Offer in Brazil to Completethe Acquisition of a Controlling Equity Stake in Brava Energia S.A.

Bogotá, July 20, 2026

Ecopetrol S.A. (BVC: ECOPETROL; NYSE: EC) announced today that its Brazilian subsidiary, Ecopetrol Investimentos do Brasil LTDA, published on the B3 Securities Exchange in Brazil the document governing the terms and conditions of the Voluntary Tender Offer (Oferta Pública de Aquisição Voluntária, or “OPAV”), incorporating the recommendations communicated by the Comissão de Valores Mobiliários (“CVM”) in Official Letter No. 160/2026/CVM/SRE/GER-1.

With the filing of this revised document, the OPAV on B3 is resumed for the acquisition of a total of 116,110,717 common shares of Brava Energia S.A. (B3: BRAV3), representing approximately 25% of its share capital.

The OPAV is expected to remain open until August 5, 2026, on which date the auction would take place. The transaction remains subject to the fulfillment of applicable regulatory requirements and certain specific conditions precedent, all of which are disclosed in the offer document published on B3.

We expect to disclose the results of the OPAV together with any other material developments related to the transaction.

Ecopetrol is the largest company in Colombia andone of the main integrated energy companies in the American continent, with more than 19,000 employees. In Colombia, it is responsiblefor more than 60% of the hydrocarbon production of most transportation, logistics, and hydrocarbon refining systems, and it holds leadingpositions in the petrochemicals and gas distribution segments. With the acquisition of 51.4% of ISA’s shares, the company participatesin energy transmission, the management of real-time systems (XM), and the Barranquilla - Cartagena coastal highway concession. At theinternational level, Ecopetrol has a stake in strategic basins in the American continent, with Drilling and Exploration operations inthe United States (Permian basin and the Gulf of Mexico), Brazil, and Mexico, and, through ISA and its subsidiaries, Ecopetrol holds leadingpositions in the power transmission business in Brazil, Chile, Peru, and Bolivia, road concessions in Chile, and the telecommunicationssector.

This release contains statements that may be consideredforward-looking statements within the meaning of Section 27A of the U.S. Securities Act of 1933, as amended, and Section 21E of the U.S.Securities Exchange Act of 1934, as amended. All forward-looking statements, whether made in this release or in future filings or pressreleases, or orally, address matters that involve risks and uncertainties, including in respect of the Company’s prospects for growthand its ongoing access 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 ofoil & gas, our exploration, and production activities, market conditions, applicable regulations, the exchange rate, the Company’scompetitiveness and the performance of Colombia’s economy and industry, to mention a few. We do not intend and do not assume anyobligation to update these forward-looking statements.

For more information, please contact:

Investor Relations Office

Email: [email protected]

Head of Corporate Communications (Colombia)

Marcela Ulloa

Email: [email protected]