The Socialist Union Party was a small De Leonist group that was active in the United States in the late 1930s and early 1940s. The group was founded by Abraham Ziegler, who had been expelled from the Socialist Labor Party in the mid-1930s and joined the Industrial Union Party, the only other De Leonist group. While the IUP once had a small following among independent unions such as the Sailors Union of the Pacific and the United Furniture Workers of America in the early 1930s, by the end of the decade this support had dried up, with those groups joining more traditional labor federations like the American Federation of Labor. With their base in the labor movement gone, the IUP was reduced to a propagandist/ educational society.