Prime Minister of Australia prime minister, otherwise William McMahon63. Robert Menzies was the oldest person to ever be prime minister, leaving office at 71 years old. The longest-serving Prime Minister was Sir Robert Menzies, who served in office twice: from 26 April 1939 to 28 August 1941, and again from 19 December 1949 to 26 January 1966. In total Robert Menzies spent 18 years, 5 months and 12 days in office. He served under the United Australia Party and the Liberal Party respectively. The shortest-serving Prime Minister was Frank Forde, who was appointed to the position on 6 July 1945 after the death of
Prime Minister of Australia John Curtin, and served until 13 July 1945 when Ben Chifley was elected leader of the Australian Labor Party. The last Prime Minister to serve out a full government term in the office was John Howard, who won the 2004 election and led his party to the 2007 election, but lost. Since then, the five subsequent Prime Ministers have been either voted out of the office mid-term by the caucuses of their own parties, assumed the office mid-term under such circumstances, or both. Prime Minister of Australia The Prime Minister of Australia is the head of government of Australia. The