Cockburn Sound is an inlet of the Indian Ocean on the coast of Western Australia. It extends from the south of the mouth of the Swan River at Fremantle for about 25 km to Cape Peron near Rockingham and is located at . The total area of the sound is about 100 km².
It is bounded on the east by the mainland and on the west by Garden Island and Carnac Island, and includes several rocky outcrops and reefs. The Gage Roads shipping channel lies to the north.