William James McWilliams (12 October 1856 – 22 October 1929) was an Australian politician who served as the inaugural leader of the Country Party, in office from 1920 to 1921.
He was a member of the House of Representatives from 1903 to 1922 and from 1928 to his death, on both occasions representing the Division of Franklin in Tasmania.
He represented five different political parties during his time in parliament, eventually seeing out his final term as an independent.