The French Section of the Workers' International (French: Section française de l'Internationale ouvrière, SFIO) was a major social democratic political party in France which was founded in 1905 and succeeded in 1969 by the present Socialist Party.
The SFIO was founded in 1905 as the French representative to the Second International, merging the Marxist Socialist Party of France led by Jules Guesde and the social-democratic French Socialist Party led by Jean Jaurès, who became the SFIO's leading figure.