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 25kms to Point Peron near Rockingham.

It is bounded on the east by the mainland and on the west by Garden Island and Carnac Island, several rocky outcrops and numerous well-developed coral reefs. Gage Roads lies to the north.

It is located at 32.2°S, 115.8°E. Its total area is about 100sqkm.

Industrial use along the mainland foreshore and a causeway built for access to the naval facilty on Garden Island have for many years caused concern for residents. In recent years however, heavy industry has reduced as urban infill has increased. As a result, the sound is being used increasingly for recreation and fishing as water quality has improved.