St Arnaud is a town in the Wimmera region of Victoria, Australia, 244 kilometres north west of the capital Melbourne. It is in the Shire of Northern Grampians local government area. At the 2021 census, St Arnaud had a population of 3,453.

The Victorian government's Wimmera Southern Mallee subregion is part of the Grampians region in western Victoria. It includes most of what is considered the Wimmera, and part of the southern Mallee region. The subregion is based on the social catchment of Horsham, its main settlement.