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 Bangladesh the longest serving prime minister in the country's history. According to the Constitution the Prime Minister is appointed by the President based upon the result of the electorates choice in parliamentary general election held by the Election Commission. The Prime Minister will be the leader of the majority party (or coalition) in the "Jatiya Sangsad" and must have the confidence of the "Jatiya Sangsad" to govern. The cabinet is composed of ministers selected by the prime minister and appointed by the president. At least 90% of the ministers must be MPs. The other 10% may be non-MP experts or "technocrats"