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
Acting prime minister if the incumbent is temporarily incapacitated. Whilst in other countries the term "Acting Prime Minister" only refers to an individual actually performing the role, in Israel the term is also in use when a designated Minister is allocated, even if they never actually perform the role. In New Zealand, the Acting Prime Minister is the designated head of government when the incumbent is not available to fulfill their duties. This includes when the Prime Minister is overseas, unwell, or otherwise temporarily unavailable. Typically this position is filled by the Deputy Prime Minister. Hugh Watt, who was then the Deputy Prime