Mount Barker is a town on Albany Highway and the administrative centre of the Shire of Plantagenet in the Great Southern region of Western Australia. At the 2021 census, Mount Barker had a population of 2,855.

The Shire of Plantagenet is a local government area in the Great Southern region of Western Australia, managed from the town of Mount Barker, 360 kilometres (224 mi) south of Perth and 50 kilometres (31 mi) north of Albany. The shire covers an area of 4,792 square kilometres (1,850 sq mi) and includes the communities of Narrikup, Rocky Gully, Kendenup and Porongurup.