6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

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

For the month of February 2026

Cosan S.A.

(Exact name of registrant as specified in its charter)

N/A

(Translation of registrant’s name into English)

Av. Brigadeiro Faria Lima, 4100, – 16th floor São Paulo, SP 04538-132 Brazil (Address of principal executive offices)

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

COSAN S.A.

CNPJ No. 50.746.577/0001-15

NIRE 35.300.177.045

Publicly Held Company

CVM Code 19836

MATERIAL FACT

COSAN S.A. (B3: CSAN3; NYSE: CSAN) (“Cosan” or “Company”), in compliance with CVM Resolution No. 44/2021, informs its shareholders and the market in general that the Company is evaluating the possibility of carrying out an initial public offering of shares issued by Compass Gás e Energia S.A. (the “Potential Offering”)

The effective completion of the Potential Offering is subject, among other factors, to domestic and international market conditions and to the obtaining of the relevant corporate approvals, and, as of this date, there is no decision regarding the effective completion of the Potential Offering.

The Company will keep the market informed of any developments related to the Potential Offering.

São Paulo, February 23, 2026.

Rafael Bergman

Chief Financial and Investor Relations Officer

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:  February 23, 2026