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 Cambodia to 1998. Elected as prime minister in his own right in 1998, he is the longest serving prime minister in Cambodian history. The position was first held by King Norodom Sihanouk in March 1945, during the French colonial administration. Cambodia's first parliamentary elections were held on 1 September 1946. The Democratic Party remained the dominant-party in Cambodian politics throughout the 1940s until the formation of the Sangkum Reastr Niyum in 1955. Sangkum was the dominant-party in Cambodia from 1955 to 1970 following a military coup by General Lon Nol. Until 1993, it was not an elected position. Merely few prime