The Commonwealth of Australia is officially established on January 1, 1901 by the Federation of six self-governing British colonies: New South Wales, Victoria, Queensland, South Australia, Western Australia, and Tasmania, creating a single nation with a federal government under the new Australian Constitution.
This process, known as Federation, united these separate colonies into states, giving them a national parliament for shared responsibilities like defense and trade. The Australian Constitution, was drafted at conventions and approved by the British Parliament.