William Dudley "Big Bill" Haywood (February 4, 1869–May 18, 1928) was a prominent figure in American radical unionism as a leader in the Western Federation of Miners (WFM) and later as a founding member of the Industrial Workers of the World (IWW).

Haywood began working in the mines at age nine where he lost his left eye. After brief stints as a cowboy and a homesteader, he returned to mining and rose through the ranks of the union to become a member of the WFM national union's General Executive Board in 1900, and editor of the union's magazine, then serving as secretary-treasurer in 1901.

In 1901, class warfare erupted in the mines of Colorado that took the lives of 33 union and non-union workers. The WFM initiated a series of strikes to combat the brutal working conditions and starvation wages. The defeat of these strikes led to Haywood's belief in "One Big Union" organized along industrial lines to bring broader working class support for labour struggles.

Late in 1904, Haywood along with over 30 other prominent labour radicals, met in Chicago to lay down plans for a new revolutionary union. A manifesto was written and sent around the country. Unionists who agreed with the manifesto were invited to attend a convention to found the new union which was to become the Industrial Workers of the World.

At 10 A.M. on June 27, 1905, Haywood addressed the crowd assembled at Brand's Hall in Chicago who had gathered to the Industrial Workers of the World founding convention. In the audience were nearly 200 delegates from organizations all over the country representing socialists, anarchists, miners, industrial unionists and rebel workers.

"Fellow Workers, this is the Continental Congress of the Working Class. We are here to confederate the workers of this country into a working-class movement in possession of the economic powers, the means of life, in control of the machinery of production and distribution without regard to capitalist masters."

Despite Haywood's involvement in the IWW, which was heavily influenced by anarcho_syndicalism, he was a longtime member of the Socialist Party of America, and often pleaded with workers to vote in elections.

In 1915, Haywood became the general secretary-treasurer of the IWW. He led massive textile strikes in Massachusetts and New Jersey, and assisted in organizing the over three million workers that at one time or another were in the IWW in this era. In 1918, Haywood was convicted of violating federal espionage and Soviet Union where he became an advisor to the Bolshevik government. Haywood died in Moscow in 1928. Half of his ashes were buried in the Kremlin and an urn containing the other half of his ashes was sent to Chicago and buried near a monument to the Haymarket anarchists.