Sir William "Billy" McMahon, (23 February 190831 March 1988), was an Australian politician who was the Leader of the Liberal Party and the 20th Prime Minister of Australia from 10 March 1971 to 5 December 1972. McMahon was a member of the Australian House of Representatives for the seat of Lowe from his election in 1949 until his resignation in 1982. He rose to power at a bad time for the Coalition after over two decades in power, and he led his government to a loss to the Labor Party led by Gough Whitlam. He was the longest continuously serving government minister in Australian history - serving 21 years and 6 months - and held the longest tenure as Prime Minister without leading his party to victory at an election, being Prime Minister for 1 year and 270 days.