Australia, officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent (the world's smallest), the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans.Neighbouring countries include Indonesia, East Timor, and Papua New Guinea to the north, the Solomon Islands, Vanuatu, and New Caledonia to the north-east, and New Zealand to the southeast.Australia is a developed country, with a prosperous multicultural society and excellent results in many international comparisons of national performance such as human development, quality of life, health care, life expectancy, public education, economic freedom, and the protection of civil liberties and political rights.Australian cities routinely rank among the world's highest in terms of cultural offerings and quality of life. It is a member of the United Nations, G20, Commonwealth of Nations, Organisation for Economic Cooperation and Development, ANZUS, Asia-Pacific Economic Cooperation, South Pacific Forum, and the World Trade Organization.