Oceania, also known as Oceanica, is a region centred on the islands of the tropical Pacific Ocean. Opinions of what constitutes Oceania range from its three subregions of Melanesia, Micronesia, and Polynesia to, more broadly, the entire insular region between Southeast Asia and the Americas, including Australasia and the Malay Archipelago.

The term is often used more specifically to denote a continent comprising Australia and proximate islands or biogeographically as a synonym for either the Australasian ecozone (Wallacea and Australasia) or the Pacific ecozone (Melanesia, Polynesia, and Micronesia, excluding both New Zealand and mainland New Guinea).