Credit Suisse chief executive Tidjane Thiam has resigned amid a power struggle which followed a spying scandal at the bank.
He is stepping down after five years at the Swiss bank just months after it emerged that two former employees had been placed under surveillance.
Mr Thiam said he did not know the spying was taking place.
His departure was to protect the bank's reputation, chairman Urs Rohner said, denying ill-feeling between the two.
The situation at the bank "became more difficult" over the past few weeks after a second case of spying emerged, Mr Rohner told Swiss radio.
"At some point we realised that we couldn't get out of this situation unless we made a change and Tidjane Thiam understood that too," he said.
