Olkhon (Russian:Ольхо́н, also transliterated as Olchon) is the fourth-largest lake-bound island in the world. It is by far the largest island in Lake Baikal in eastern Siberia, with an area of 730 square kilometres (280 sq mi). Structurally, it acts as the southwestern margin of Academician Ridge. The island measures 71.5 km (44.4 mi) in length and 20.8 km (12.9 mi) in width.