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 March 2026

Commission File Number: 001-15092

TURKCELL İLETİŞİM HİZMETLERİ A.Ş.

(Translation of registrant’s name into English)

Aydınevler Mahallesi İnönü Caddesi No:20

Küçükyalı Ofispark

34854 Maltepe
Istanbul, Türkiye

(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:

x Form 20-F  ¨ Form 40-F

Turkcell İletişim Hizmetleri A.Ş. hereby furnishes to the Securities and Exchange Commission the information set forth in the following Exhibit Index. The attached annual report is the translation of an Annual Report that was prepared in accordance with the Capital Markets Board of Türkiye, and includes certain financial information prepared in accordance with Turkish Accounting Standards (“TAS”) / Turkish Financial Reporting Standards (“TFRS”) and audited in accordance with standards on auditing as issued by the Capital Markets Board of Türkiye and Independent Auditing Standards which are part of the Turkish Auditing Standards as issued by the Public Oversight Accounting and Auditing Standards Authority of Türkiye.

EXHIBIT INDEX

SIGNATURES

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