Brookton Highway is a 112-kilometre (70 mi) long undivided single carriageway highway in Western Australia, running from the southern Perth suburb of Kelmscott, through Westdale, to the southern Wheatbelt town of Brookton. It is signposted as State Route 40; however, the route and highway continue on far past Brookton, passing through Corrigin, Kondinin, Hyden, Lake King, and finishing at South Coast Highway, just west of Ravensthorpe.

Kelmscott is a southeastern suburb of Perth, Western Australian within the local government area of the City of Armadale. It is 23 kilometres (14 mi) southeast of Perth along the Albany Highway.