Lake Colac is a large freshwater lake in western Victoria, Australia. The town of Colac is built along the south shore of the lake. Lake Colac has an area of 1,820 hectares, an average depth of 2.5 metres and a circumference of 33 km. The area was the home of the Kolijon (or Coladjin) people. The name "Colac" comes from either the word "Kolijon", or their word "kolak" which means the lake's sand or fresh water.