Mainland Australia is the main landmass of the Australian continent, excluding the Aru Islands, New Guinea, Tasmania, and other Australian offshore islands. The landmass also constitutes the mainland of the territory governed by the Commonwealth of Australia, and the term, along with continental Australia, can be used in a geographic sense to exclude surrounding continental islands and external territories. Generally, the term is applied to the states of New South Wales, Queensland, South Australia, Victoria, and Western Australia, as well as the Australian Capital Territory, Jervis Bay Territory, and Northern Territory.

The continent of Australia, sometimes known in technical contexts by the names Sahul, Australia-New Guinea, Australinea, or Meganesia to distinguish it from the country of Australia, is located within the Southern and Eastern hemispheres. The continent includes mainland Australia, Tasmania, the island of New Guinea, the Aru Islands, the Ashmore and Cartier Islands, most of the Coral Sea Islands, and some other nearby islands. Situated in the geographical region of Oceania, Australia is the smallest of the seven traditional continents.