largest of the D'Entrecasteaux Islands, Papua New Guinea, in the southwestern Pacific Ocean. The island lies 30 miles (50 km) across Ward Hunt Strait from the southeastern tip of New Guinea, in the Solomon Sea. It is separated from Goodenough Island (northwest) by Moresby Strait and from Normanby Island (southeast) by Dawson Strait. The volcanic island, measuring 40 by 30 miles (65 by 48 km), has an area of 519 square miles (1,345 square km).

Rising to 6,801 feet (2,073 metres) near Wadalei in the northeast, Fergusson Island is drained by numerous short streams. Although the central volcanic peak is extinct, there are signs of its former activity, including geysers and fumaroles. Seymour Bay is located on the west coast, Sebutuia Bay on the east, and Hughes Bay on the north. The principal settlements, Salamo and Mapamoiwa, are on the southern coast. Gold deposits at Wapolu on the north coast were worked briefly in the mid-1990s.