The Nationalist Party of Australia was an Australian political party. It began on 17 February 1917 when the conservative Commonwealth Liberal Party and the National Labor Party (NLP) joined together. The Nationalist Party held government until 1929. It was the major opposition to the Labor party. In 1931 it joined with a group who left the Labor Party led by Joseph Lyons and became the United Australia Party. This was the basis of the Liberal Party of Australia which began in 1944.