UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 6-K

REPORT OF FOREIGN ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of October, 2015

Commission file number: 1-10110

BANCO BILBAO VIZCAYA ARGENTARIA, S.A.

(Exact name of Registrant as specified in its charter)

BANK BILBAO VIZCAYA ARGENTARIA, S.A.

(Translation of Registrant’s name into English)

Calle Sauceda 28

28050 Madrid

Spain

(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:

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

Banco Bilbao Vizcaya Argentaria, S.A. (BBVA), in compliance with the Securities Market legislation, hereby proceeds by means of the present document to notify the following:

RELEVANT EVENT

Further to the relevant events dated 18^th and 30^th September, 2015, and 19^th October, 2015, BBVA hereby communicates that, on 29^th October, 2015, the Spanish National Securities Market Commission has authorized the admission to listing of the new shares of the free-of-charge capital increase resolved by the Ordinary General Meeting of BBVA shareholders held on 13^th March, 2015, under agenda item four, section 4.2, and executed by the Board of Directors in its 30^th September, 2015 meeting, corresponding to the shareholder remuneration system called “Dividend Option”, being the new shares allocated to shareholders.

The authorization for the admission to listing of the new shares in the Spanish Stock Exchanges, through the Spanish SIBE electronic trading platform (Sistema de Interconexión Bursátil Español), is expected to be granted as of today, 30^th October, 2015, so that ordinary trading of such shares in the Spanish Stock Exchanges will commence on 2^nd November, 2015.

Madrid, 30^th October, 2015

SIGNATURE

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.