This article charts the historical emergence of an international anarcho-syndicalist current from the beginning of the twentieth century up to the 1930s. It is especially after the First World War and the Russian Revolution of 1917, that syndicalists (or revolutionary unionists), among which were many libertarians, had to specify the meaning of the revolution they advocated. One part joined up with Bolshevism while the other, underlining its anti-authoritarian and federalist dimension, formed an anarcho-syndicalist current. This process led to the foundation in 1922 of the International Workers’ Association (IWA, taking over the name of the First International in reference to its anti-authoritarian tendency), which still exists today despite its marginalisation since the 1930s.