Jean Léon Jaurès (September 3, 1859 - July 31, 1914) was a French Socialist leader. He was one of the first social democrats, differentiating his French Socialist Party from those taking advocating revolutionary class war and strict communism.
He was born at Castres (Tarn) and educated at the lycée Louis-le-Grand and the école normale supérieure. He took his degree as associate in philosophy in 1881. After teaching philosophy for two years at the lycée of Albi (Tarn), he lectured at the University of Toulouse. He was elected republican deputy for the département of Tarn in 1885. In 1889, after unsuccessfully contesting Castres, he returned to his professional duties at Toulouse, where he took an active interest in municipal affairs, and helped to found the medical faculty of the university. He also prepared two theses for his doctorate in philosophy, De primis socialismi germanici lineamentis apud Lutherum, Kant, Fichte et Hegel (1891), and De la réalité du monde sensible.
In 1902 he gave energetic support to the miners of Carmaux who went out on strike in consequence of the dismissal of a socialist workman, Calvignac; and in the next year he was re-elected to the chamber as deputy for Albi. Although he was defeated at the election of 1898 and was for four years outside the chamber, his eloquent speeches made him a force in politics as an intellectual champion of socialism. He edited the Petite Republique, and was one of the most energetic defenders of Alfred Dreyfus. He approved of the inclusion of Alexandre Millerand, the socialist, in the Waldeck-Rousseau ministry, though this led, to a split with the more revolutionary section led by Jules Guesde.
In 1902 he was again returned as deputy for Albi, and during the Combes administration his influence secured the coherence of the radical-socialist coalition known as the bloc. In 1904 he founded the socialist paper, L'Humanité. The French socialist groups held a congress at Rouen in March 1905, which resulted in a new consolidation; the new party, headed by Jaurès and Guesde, ceased to co-operate with the radicals and radical-socialists, and became known as the unified socialists, pledged to advance a collectivist programme. At the general elections of 1906, Jaurès was again elected for the Tarn. His ability was now generally recognized; but the strength of the socialist party still had to reckon with the equally practical and vigorous liberalism of Georges Clémenceau, who was able to appeal to his countrymen (in a notable speech in the spring of 1906) to rally to a radical programme which had no socialist Utopia in view. Clemenceau's image as a strong and practical radical leader considerably diminished the effect of the socialist propaganda. Jaurès, in addition to his daily journalistic activity, published Les preuves; affaire Dreyfus (1900); Action socialiste (1899); Etudes socialistes (1902), and, with other collaborators, Histoire socialiste (1901), etc.
A committed pacifist who wished to prevent by diplomatic means what became the First World War, Jean Jaurès was assassinated in a Paris café by Raoul Vilain on July 31, 1914, one day before the mobilizations that began the war.