The Workers' International Industrial Union (WIIU) was a Revolutionary Industrial Union headquartered in Detroit in 1908 by radical trade unionists closely associated with the Socialist Labor Party of America, headed by Daniel DeLeon. The organization was formed when it broke with the main faction of the Industrial Workers of the World (IWW) over the question of political action.
After seven years of parallel existence as the so-called "Detroit IWW," the dissident organization changed its name to Workers' International Industrial Union in 1915. The WIIU maintained a presence in the United States, Canada, Britain and Australia before its ultimate dissolution in 1925.