Thetis Island (population: 350) is an island and unincorporated community off the coast of British Columbia, Canada, lying between Vancouver Island, which is to the west across Stuart Channel, and the west from the north tip of Galiano Island, from which it is separated by Trincomali Channel. With its immediate southern neighbour Penelakut Island (formerly Kuper Island), it is one of the Gulf Islands. Thetis island is 2,560 acres (4 sq. miles)in size. It is approximately 2 miles wide and 3 miles long north to south. Two north to south land ridges define the east and west sides of the island.