federation of workers' groups that, despite ideological divisions within its ranks, had a considerable influence as a unifying force for labour in Europe during the latter part of the 19th century.

The First International was founded under the name of International Working Men's Association at a mass meeting in London on Sept. 28, 1864. Its founders were among the most powerful British and French trade-union leaders of the time. Though Karl Marx (Marx, Karl) had no part in organizing the meeting, he was elected one of the 32 members of the provisional General Council and at once assumed its leadership. The International came to assume the character of a highly centralized party, based primarily on individual members, organized in local groups, which were integrated in national federations, though some trade unions and associations were affiliated to it collectively. Its supreme body was the Congress, which met in a different city each year and formulated principles and policies. A General Council elected by the Congress had its seat in London and served as the executive committee, appointing corresponding secretaries for each of the national federations; organizing collections for the support of strikes in various countries; and, in general, advancing the International's goals.

From its beginnings, the First International was riven by conflicting schools of socialist thought—Marxism, Proudhonism (after Pierre-Joseph Proudhon, who advocated only the reform of capitalism), Blanquism (after Auguste Blanqui, who advocated radical methods and a sweeping revolution), and Mikhail Bakunin's (Bakunin, Mikhail Aleksandrovich) version of anarchism, which dominated the International's Italian, Spanish, and French-Swiss federations. The First International split at its Hague Congress in 1872 over the clash between Marx's centralized socialism and Bakunin's anarchism. In order to prevent the Bakuninists from gaining control of the association, the General Council, prompted by Marx, moved its headquarters to New York City, where it lingered until it was formally disbanded at the Philadelphia Conference in July 1876. The Bakuninists, assuming leadership of the International, held annual congresses from 1873 to 1877. At the Ghent Socialist World Congress in 1877, the Social Democrats broke away because their motion to restore the unity of the First International was rejected by the anarchist majority. The anarchists failed, however, to keep the International alive. After the London anarchist Congress of 1881, it ceased to represent an organized movement. The International was early proscribed in such countries as Germany, Austria, France, and Spain. French and German proposals that it be outlawed by concerted European action failed, however, because of British reluctance to suppress the General Council in London. It should be noted that the International's renown at the time as a formidable power with millions of members and almost unlimited resources was out of proportion with the association's actual strength; the hard core of its individual members probably seldom exceeded 20,000. Although so accused, it did not organize the wave of strikes that swept France, Belgium, and Switzerland in 1868, but its support and rumoured support of such strikes was very influential.