Australia, officially the Commonwealth of Australia, is a country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. It is the largest country by area in Oceania and the sixth-largest in the world. It is the world's oldest, flattest, and driest inhabited continent, with some of the least fertile soils. It is a megadiv…Australia, officially the Commonwealth of Australia, is a country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. It is the largest country by area in Oceania and the sixth-largest in the world. It is the world's oldest, flattest, and driest inhabited continent, with some of the least fertile soils. It is a megadiverse country, and its size gives it a wide variety of landscapes and climates including deserts and tropical rainforests.