Bank Leu AG was a Swiss private bank that existed from 1755 to 2007. Headquartered in Zurich, it was a subsidiary of Crédit Suisse from 1990. In 2007, it was merged with that company's other private banking units as Clariden Leu. At the time, it was the oldest bank in Switzerland.

The bank was founded in 1758 as Leu et Compagnie, named after its founder, Johann Jacob Leu, who later became mayor of Zurich. Originally a state-owned bank, it was privatized in 1798 after Napoleon conquered Switzerland; the bank's officials did not want its assets to be taken over by Napoleon's new client state, the Helvetic Republic. In 1854, it incorporated as Leu & Co. after more than a century as a limited partnership. It became a public limited company in 1969.