Auguste Marie Joseph Jean Léon Jaurès, commonly referred to as Jean Jaurès, was a French Socialist leader. Initially a Moderate Republican, he later became one of the first social democrats and the leader of the French Socialist Party, which opposed Jules Guesde's revolutionary Socialist Party of France. The two parties merged in 1905 in the French Section of the Workers' International (SFIO). An antimilitarist, Jaurès was assassinated in 1914 at the outbreak of World War I, but remains one of the main historical figures of the French Left. As a heterodox Marxist, Jaurès rejected the concept of the dictatorship of the proletariat and tried to conciliate idealism and materialism, individualism and collectivism, democracy and class struggle, patriotism and internationalism.

Jules Bazile, known as Jules Guesde was a French socialist journalist and politician.