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. It is part of the South West Land Division of Western Australia, with the majority 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.

Western Australia is a state of Australia occupying the western third of the land area of Australia, excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. With a total land area of 2,527,013 square kilometres (975,685 sq mi), Western Australia is Australia's largest state as well as the second-largest subdivision of any country on Earth, surpassed only by the Sakha Republic in eastern Russia. As of 2021, the state has 2.76 million inhabitants—11 percent of the national total. The vast majority live in the south-west corner; 79 percent of the population lives in the Perth area, leaving the remainder of the state sparsely populated.