Ko Island (小島, Ko-jima) or Kojima is an uninhabited island in the Sea of Japan, 23 kilometres (14 mi) southwest of the mainland portion of the town of Matsumae town and is the southernmost point in Hokkaidō. It is under the administration of the town of Matsumae in Matsumae District, Oshima Subprefecture in Hokkaidō, Japan.