Western Port, commonly but unofficially known as Western Port Bay, is a large tidal bay in southern Victoria, Australia, opening into Bass Strait. It is the second largest bay in the state. Geographically, it is dominated by two large islands; French Island and Phillip Island. At the time it was renamed, its position was west of other known ports and bays, but Western Port has become something of a misnomer as it lies just to the east of the larger Port Phillip and the city of Melbourne. It is visited by Australian fur seals, whales and dolphins, as well as many migratory waders and seabirds. It is listed under the Ramsar Convention as a wetland of international significance.

Bass Strait is a strait separating the island state of Tasmania from the Australian mainland. The strait provides the most direct waterway between the Great Australian Bight and the Tasman Sea, and is also the only maritime route into the economically prominent Port Phillip Bay.