Australasia is a region of Oceania: Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean (Island Melanesia, potentially including Wallacea). The term was coined by Charles de Brosses in Histoire des navigations aux terres australes (1756). He derived it from the Latin for "south of Asia" and differentiated the area from Polynesia (to the east) and the southeast Pacific (Magellanica). It is also distinct from Micronesia (to the northeast). Australasia sits on the Indo-Australian Plate, together with India.

Geopolitically, Australasia is sometimes used as a term for Australia and New Zealand together in the absence of another word limited to those two countries. Sometimes the island of New Guinea (Papua New Guinea and the Indonesian part of the island) is encompassed by the term

Alternate versions of Australasia or similar have been discovered in the multiverse:

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