The Australian republic referendum held on 6 November 1999 was a two-question referendum to amend the Constitution of Australia. The first question asked whether Australia should become a republic with a President appointed by Parliament following a bi-partisan appointment model which had been approved by a half-elected, half-appointed Constitutional Convention held in Canberra in February 1998. The second question, generally deemed to be far less important politically, asked whether Australia should alter the Constitution to insert a preamble. For some years opinion polls had suggested that a majority of the electorate favoured a republic. Nonetheless, the republic referendum was defeated, partly due to division among republicans on the method proposed for selection of the president and dissident republicans opposed the president to have strong executive power.

Head of the Commonwealth is a title used by the ceremonial leader who symbolises "the free association of independent member nations" of the Commonwealth of Nations, an intergovernmental organisation that currently comprises fifty-four sovereign states. There is no set term of office or term limit and the role itself involves no part in the day-to-day governance of any of the member states within the Commonwealth. The title has been held by the reigning British monarch since its establishment.

By 1949, the British Commonwealth was a group of eight countries, each having King George VI as monarch. India, however, desired to become a republic, but not to leave the Commonwealth by doing so. This was accommodated by the creation of the title Head of the Commonwealth for the King, and India became a republic in 1950. Subsequently, many other nations including Pakistan, Sri Lanka, Ghana and Singapore ceased to recognise the monarch of the United Kingdom as their respective head of state, but recognised the British monarch as Head of the Commonwealth as members of the Commonwealth of Nations.The title is currently held by Queen Elizabeth II, George VI's elder daughter. Charles, Prince of Wales, was appointed her designated successor at the Commonwealth Heads of Government Meeting 2018.