Bair, who ran the Federal Deposit Insurance Corporation (FDIC) from 2006 to 2011, was appointed to the board of the euro zone's biggest bank, which is making a big push in the United States, 18 months ago.

Her departure leaves just two non-Spaniards on its board: Mexican Carlos Fernandez Gonzalez and Bruce Carnegie-Brown of Britain.

(Reporting by Sonya Dowsett; Editing by Mark Potter)