The Fremantle Outer Harbour is the part of Fremantle Harbour located in the Cockburn Sound, at the City of Kwinana, Western Australia. Fremantle Harbour consists of the Inner Harbour, which is situated on the mouth of the Swan River; and the Outer Harbour, which is 20 km to the south. It is managed by the Fremantle Port Authority.

Fremantle Harbour is Western Australia's largest and busiest general cargo port and an important historical site. The inner harbour handles a large volume of sea containers, vehicle imports and livestock exports, cruise shipping and naval visits, and operates 24 hours a day. It is located adjacent to the city of Fremantle, in the Perth metropolitan region.