Thwaites Glacier (), sometimes referred to as the Doomsday Glacier, is an unusually broad and vast Antarctic glacier flowing into the Pine Island Bay, part of the Amundsen Sea, east of Mount Murphy, on the Walgreen Coast of Marie Byrd Land. Its surface speeds exceed near its grounding line. Its fastest flowing grounded ice is centred between east of Mount Murphy. It was named by the Advisory Committee on Antarctic Names in 1967 after Fredrik T. Thwaites (1883-1961), a glacial geologist, geomorphologist and professor emeritus at the University of Wisconsin-Madison. The historian Reuben Gold Thwaites was his father.