Great Southern Highway is a highway in the Southern Wheatbelt region of Western Australia, starting from Great Eastern Highway at The Lakes, 50 km from Perth, and ending at Albany Highway near Cranbrook. It is the primary thoroughfare for this part of Western Australia and runs parallel with the Perth-Albany railway for its entire length. It is signed as State Route 120 from York to Cranbrook, and was first named in 1949, although it was built well before that time.