Australia, officially the Commonwealth of Australia, [17] is a country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. [18] Australia has a total area of 7,688,287 km 2 (2,968,464 sq mi), making it the sixth-largest country in the world and the largest in Oceania.It is the world's oldest, [19] flattest, [20] and driest inhabited ...