Question: who was the longest serving australian prime minister
Answer: 12th Sir Robert Menzies ( 1894 -- 1978 ) United Australia Kooyong , VIC ( 1934 -- 1966 ) 26 April 1939 29 August 1941 7002856000000000000 ♠ 2 years , 125 days 18 years , 163 days 1940 1949 1951 1954 1955 1958 1961 1963 Liberal 19 December 1949 26 January 1966 7003588200000000000 ♠ 16 years , 38 days 2 .