The South West region is one of the nine regions of Western Australia. It is so named because it is located in the south-west corner of Western Australia. The South West region has an area of 23,970 km², and a population of about 123,000 people.

Southwest Australia is a biodiversity hotspot that includes the Mediterranean forests, woodlands, and scrub ecoregions of Western Australia. The region has a wet-winter, dry-summer Mediterranean climate, one of five such regions in the world. The region covers 356,717 km², consisting of a broad coastal plain 20-120 kilometres wide, transitioning to gently undulating uplands made up of weathered granite, gneiss and laterite. Desert and xeric shrublands lie to the north and east across the centre of Australia, separating Southwest Australia from the other Mediterranean and humid-climate regions of the continent.

The Southwest is a loosely defined area in the southwest corner of Western Australia. Various regionalisations have provided formal definitions of the area, but these do not coincide.