New Guinea is the world's second-largest island, with an area of 785,753 km² (303,381 sq mi). Located in Melanesia in the southwestern Pacific Ocean, the island is separated from Australia by the 150-kilometre wide Torres Strait, though both landmasses lie on the same continental shelf, and were united during episodes of low sea level in the Pleistocene glaciations as the combined landmass of Sahul. Numerous smaller islands are located to the west and east. The island's name was given by Spanish explorer Yñigo Ortiz de Retez during his maritime expedition of 1545 due to the resemblance of the indigenous peoples of the island to those in the African region of Guinea.