The Amundsen Sea is an arm of the Southern Ocean off Marie Byrd Land in western Antarctica. It is bounded by Cape Flying Fish, the northwestern tip of Thurston Island to the east and Cape Dart on Siple Island to the west. East of Cape Flying Fish starts the Bellingshausen Sea. West of Cape Dart is no named marginal sea of the Southern Ocean between Amundsen Sea and Ross Sea. Named for the Norwegian polar explorer Roald Amundsen by the Norwegian expedition of 1928-29, under Captain Nils Larsen, while exploring this area in February, 1929.