A type of anarchism which maintains that an anarchist society can come about through action by workers organised in unions - typically grassroots unions with direct democracy or without officials. Workers' organisation is to culminate in a general strike which overcomes capitalism, as well as generating day-to-day resistance which weakens capitalist control.
The IWW and IWA have always been the main anarcho-syndicalist groups.
The IWW, or Wobblies
, believed in the formation of one big union involving all workers, as a prelude to a general strike. They still exist, but were most successful in pre-WW2 America, when they successfully organised many workers.
The IWA is an international federation of groups of anarcho-syndicalists in various countries. Unlike the IWW, it organises as a federation of individuals and not as a union divided up into industries and occupations.
The Spanish union, CGT, is federated to the IWA and is the largest syndicalist group anywhere today. It was even bigger in the 30s, when it was one of the main organisers of the resistance to Franco's attempt to seize power. It provoked controversy, however, by entering government, in breach of anarchist principles.