Vikram Pandit, who was named chief executive of Citigroup Inc. on the eve of the financial crisis and led the bank through a bruising five-year stretch that included a $45 billion federal rescue, abruptly stepped down Tuesday.

Mr. Pandit, 55 years old, departed following a clash with the board over strategy and performance, according to senior bank executives and advisers. Citigroup, the nation's third-largest bank by assets, named Citigroup veteran Michael Corbat, 52, as Mr....