Perth is the capital city of Western Australia. It is the fourth-most-populous city in Australia, with a population of over 2.3 million within Greater Perth as of 2023. The world's most isolated major city by certain criteria, Perth is part of the South West Land Division of Western Australia, with most of Perth's metropolitan area on the Swan Coastal Plain between the Indian Ocean and the Darling Scarp. The city has expanded outward from the original British settlements on the Swan River, upon which its central business district and port of Fremantle are situated.