Colac is a town in the western district of Victoria, Australia. It is about 150 kilometres (93 mi) south-west of Melbourne, on the southern shore of Lake Colac and the surrounding volcanic plains, approximately 40 kilometres (25 mi) inland from Bass Strait. Colac is the largest city in and administrative centre of the Colac Otway Shire. At June 2016, Colac had a population of 12,411.