Old Windsor Lock is a lock on the River Thames in England on the right bank beside Old Windsor, Berkshire. The lock marks the downstream end of the New Cut, a meander cutoff built in 1822 by the Thames Navigation Commissioners which created Ham Island. The lock and a wider footbridge give access to the island. Two weirs are associated; the smaller adjoins and the larger is upstream. The lock is the ninth lowest of the forty-five on the river.

Old Windsor is a large village and civil parish, in the Royal Borough of Windsor and Maidenhead, in Berkshire, England. It is bounded by the River Thames to the east and the Windsor Great Park to the west.