The Nationalist Party of Australia was an Australian political party. It was formed on 17 February 1917 from a merger between the conservative Commonwealth Liberal Party and the National Labor Party, the name given to the pro-conscription defectors from the Australian Labor Party led by Prime Minister Billy Hughes. The Nationalist Party held government (at times in coalition) until 1929. From then it was the major opposition to the Labor party until it merged with pro-Joseph Lyons Labor defectors to form the United Australia Party in 1931, which was the predecessor to the 1944 foundation of the Liberal Party of Australia.