Robert Menzies
He was Prime Minister for a total of 18 and half years which is the longest in Australia's history. After the death of Joseph Lyons he was elected leader of the United Australia Party and became Prime Minister in 1939. He resigned in 1941 after a lot of criticism. In 1944 he helped form the new Liberal Party. In 1949 he was re-elected Prime Minister. He stayed in the job until he retired in 1966.