The One Big Union was a concept which emerged in the late 19th and early 20th century amongst working class trade unionists. The idea was that all workers should be organised in one union: one big union.

When working class unions organised they intitially organised as craft or trade unions. These organised workers by their job type: all those who drew pins in one union; and, all those who flattened pin heads in another. Capitalists could often divide craft and trade unionists along these lines in demarkation disputes. As capitalist enterprises and state bureaucracies became more centralised and larger, some workers felt that their institutions needed to become similarly large. Initiatives for One Big Union occurred across the world. Most notable was the attempt of the Industrial Workers of the World (IWW) to organise One Big Union in America and Australia.

While attempts to organise One Big Union on militant and revolutionary lines did not succeed, the unions which made the attempt like the IWW or CNT were often successful in their own right without becoming the One Big Union.

Later, in the mid-twentieth century, many trade and craft unions emulated the earlier attempts to form One Big Union by federating or conferring. Examples include the AFL-CIO in America, the TUC in England. In Canada there was a union simply called "One Big Union." Perhaps the earliest example of an alliance of trade unions exists in the ACTU (Australia).

See also

• General union
• World Federation of Trade Unions
• Anarcho-syndicalism