The Industrial Workers of the World (IWW), members of which are commonly termed "Wobblies", is an international labor union that is founded in Chicago in 1905.

The origin of the nickname "Wobblies" is uncertain.

IWW ideology combines general unionism with industrial unionism, as it is a general union, subdivided between the various industries which employ its members

The philosophy and tactics of the IWW are described as "revolutionary industrial unionism", with ties to socialist, syndicalist, and anarchist labor movements.

In the 1910s and early 1920s, the IWW achieved many of their short-term goals, particularly in the American West, and cute across traditional guild and union lines to organize workers in a variety of trades and industries.

At their peak in August 1917, IWW membership is estimated at more than 150,000, with active wings in the United States, Canada, and Australia.

The extremely high rate of IWW membership turnover during this era (estimated at 133% per decade) makes it difficult for historians to state membership totals with any certainty, as workers tend to join the IWW in large numbers for relatively short periods (e.g., during labor strikes and periods of generalized economic distress). 

Membership declines dramatically in the late 1910s and 1920s.

There are conflicts with other labor groups, particularly the American Federation of Labor (AFL), which regards the IWW as too radical, while the IWW regards the AFL as too conservative and opposed their decision to divide workers on the basis of their crafts.

Membership also decline due to government crackdowns on radical, anarchist and socialist groups during the First Red Scare after the First World War.

In Canada, the IWW is outlawed by the federal government by an Order in Council on September 24, 1918.

Probably the most decisive factor in the decline in IWW membership and influence is a 1924 schism in the organization, from which the IWW never fully recovers.

The IWW promotes the concept of "One Big Union", and contends that all workers should be united as a social class to supplant capitalism and wage labor with industrial democracy.

It is known for the Wobbly Shop model of workplace democracy, in which workers elect their own managers and other forms of grassroots democracy (self-management) are implemented

The IWW does not require its members to work in a represented workplace, neither does it exclude membership in another labor union.