Constitution of Australia

The Constitution of Australia is the supreme law of Australia. It is a written constitution that sets down the political structure of Australia as a federation under a constitutional monarchy governed with a parliamentary system and outlines the structure and powers of the Commonwealth of Australia's three constituent parts: the executive, legislature, and judiciary.

The Constitution was drafted between 1891 and 1898 through a series of conventions conducted by representatives of the six self-governing British colonies in Australia: New South Wales, Queensland, South Australia, Tasmania, Victoria and Western Australia. The final draft was then approved in a set of referendums from 1898 to 1900. The British government objected to some elements of the final draft, but a slightly modified form was enacted as section 9 of the Commonwealth of Australia Constitution Act 1900, an Act of the Parliament of the United Kingdom, and given royal assent on 9 July 1900. This Act, also known as the covering Act, also authorised the Queen to proclaim the actual act of federation, which was done by Queen Victoria on 17 September 1900, to take effect on 1 January 1901. After this, the six colonies became states within the new federation.

The High Court of Australia is responsible for the interpretation of the Constitution, their decisions forming the basis of Australian constitutional law. As well as its textual provisions, the Constitution is understood to incorporate various unwritten constitutional conventions and ideas derived from the Westminster system, one of which is responsible government. Under traditional legal theory, the Constitution is binding by virtue of the UK parliament's paramount authority over Australian law; however, various members of the High Court and some academics have expressed the view that the Constitution now derives its legal authority from the Australian people. Others contend this question is ultimately not a legal one, with the binding force of the Constitution the grundnorm ('basic norm') or starting premise of the Australian legal system. Other documents of constitutional significance to Australia include the Statute of Westminster and the Australia Act 1986.

The document may only be amended by referendum, through the procedure set out in section 128. This requires a double majority – a nationwide majority as well as a majority of voters in a majority of states. Only eight of the 45 proposed amendments put to a referendum have passed. Proposals to amend the document to recognise Indigenous Australians and to become a republic are the subject of significant contemporary debate. A proposal to establish an Indigenous Voice to Parliament was rejected in a referendum on 14 October 2023.