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 Brazil appointment) could sometimes come into conflict. 19th century abolitionist leader and historian Joaquim Nabuco said: The shortest prime-ministership was the first of the three periods of Zacarias Góis e Vasconcellos in office, when he occupied the presidency of the Council for just a few days in May 1862 before being replaced. The longest continuous prime-ministership corresponded to the period when the Viscount of Rio Branco was in office: he served as President of the Council from March 1871 until June 1875. The Viscount of Rio Branco served as Prime Minister only once, however, and his period of service as Prime