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 January, 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)

Paseo de la Castellana, 81

28046 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 notifies the following:

RELEVANT EVENT

Today BBVA has signed an agreement to sell 4.9% in China CITIC Bank Corporation Limited (CNCB) to UBS AG, London Branch (UBS), who has entered into transactions pursuant to which such CNCB shares will be transferred to a third party and the ultimate economic benefit of ownership of such CNCB shares will be transferred to Xinhu Zhongbao Co., Ltd (Xinhu) (the Relevant Transactions).

The selling price to UBS is HK$ 5.73 per share, amounting to a total of HK$ 13,136 million, equivalent to approximately 1,460 million Euros¹. After completing the sale BBVA will hold a 4.7% interest in CNCB.

The closing of this transaction between UBS and BBVA will happen after the legal and corporate requirements necessary for the Relevant Transactions relating to Xinhu have been completed. We estimate that the closing of the BBVA transaction will take place within the first quarter of 2015.

The estimated impact on the consolidated financial statements of the BBVA Group will be a net capital gain of approximately 400 million Euros. The sale will generate a positive impact on the Common Equity Tier 1 fully loaded ratio of more than 20 bp, equivalent to a capital generation of approximately 800 million Euros.

Madrid, 23 January, 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.