Australasia is a region of Oceania: Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. 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 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 (including Papua New Guinea and the Indonesian part of the island) is encompassed by the term. There are many organizations whose names are prefixed with "(Royal) Australasian Society" that are limited to just Australia and New Zealand.
In the past, Australasia has been used as a name for combined Australia/New Zealand sporting teams. Examples include tennis between 1905 and 1915, when New Zealand and Australia combined their best players to compete in the Davis Cup international tournament (and won it in 1907, 1908, 1909, 1911 and 1914), and at the Olympic Games of 1908 and 1912 Summer Olympics.