Shawnigan Lake is a lake on southern Vancouver Island, located to the west of Saanich Inlet and to the south of the Cowichan Valley region. It is the location of the village of Shawnigan Lake, British Columbia. Bedrock around the southern two-thirds of the lake is meta-igneous rock of Lower Paleozoic age which is rich in mafic minerals except along southeastern shores where felsic minerals dominate. Bands of marble up to several meters thick are scattered within this metamorphic complex. Around northern shores are volcanic rocks of variable composition from the Jurassic period.