Australasia, geographical term that has never had a precise definition and that was originally employed to denote land believed to exist south of Asia. In its widest sense it has been taken to include, besides Australia (with Tasmania) and New Zealand, the Malay Archipelago, the Philippines, Melanesia (New Guinea and the island groups lying east and southeast of it as far as and including New Caledonia and Fiji), Micronesia, and Polynesia (the scattered groups of islands extending eastward from the above groups to about longitude 130°). The Hawaiian Islands and even Antarctica have been included under the heading “Australasia,” but more often the region is treated as coterminous with Oceania.