Australasia is the area that includes Australia, New Zealand, New Guinea, and the many smaller islands in the vicinity, most of which are the eastern part of Indonesia. The name 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 and the south east Pacific (Magellanica). Australasia is sometimes used as a term for Australia and New Zealand alone, in the absence of another word limited to those two countries.
In the political sense, the word has little utility, as although Australia and New Zealand are both relatively wealthy, predominantly English-speaking countries and alike in many ways, they share little in common with the other nations in the area. The term is unpopular in New Zealand because it is seen to emphasise Australia; instead, the term Oceania is preferred, although this has a rather different meaning.
From a biological point of view, however, Australasia is a distinct region with a common evolutionary history and a great many unique plants and animals, some of them common to the entire area, others specific to particular parts but sharing a common ancestry.
The biological dividing line from Asia is the Wallace line, which represents the boundary between the two continental plates. Sulawesi and Lombok lie on the eastern, Australasian side of the line and Borneo and Bali lie on the western, Asian side.
In the past, Australasia has been used as a name for a combined Australia and New Zealand team. Examples include in 1905, when Australia and New Zealand combined its best tennis players to compete in the Davis Cup international tournament, and at the Olympic Games of 1908 and 1912.