Auguste Marie Joseph Jean Léon Jaurès, commonly referred to as Jean Jaurès (September 3, 1859 – July 31, 1914), is a French Socialist leader.

Initially a moderate republican, he is later one of the first social democrats, becoming the leader, in 1902, of the French Socialist Party, which opposes Jules Guesde's revolutionary Socialist Party of France.

The two parties merge in 1905 in the French Section of the Workers' International (SFIO).

An antimilitarist, Jaurès is assassinated at the outbreak of the First World War and remains one of the main historical figures of the French Left.