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.