French Workers' Party

The party broke away from the Federation of the Socialist Workers' Party of France (FTSF), founded in 1879. The English-language source states that Guesde and Lafargue created the party in 1880 and that its programme, written by Guesde with input from Marx, Engels and Lafargue, was approved at the opening congress. The French-language source states that at the Saint-Étienne workers' congress of 1882 the 23 Guesdist delegates split from Paul Brousse's reformist 'possibilists' and met at Roanne in September to found the Parti ouvrier (PO), so the founding year differs between the sources. It began publishing the weekly Le Socialiste in 1885 and took the name French Workers' Party in 1893.

Membership was 2,000 in 1889, 10,000 in 1893 and about 16,000 around 1898, while its vote grew from 25,000 in 1889 to 295,000 in 1898, 40 per cent of the socialist vote. Sixty per cent of members were textile, metal and building workers, and the Nord and Pas-de-Calais were its strongest areas. It won Roubaix, Montluçon and other towns in the municipal elections of 1892, and in the 1893 general election five of its members, Guesde among them, entered the Chamber of Deputies. Marcel Cachin joined in 1891.

When the socialist Alexandre Millerand entered the Waldeck-Rousseau cabinet in 1899, the party declared a return to revolutionary principles, but most of its deputies did not follow and were expelled or left. In 1902 it merged with the Blanquist Revolutionary Socialist Party and others to form the Socialist Party of France (PSdF), which in 1905 united with Jean Jaurès's French Socialist Party (PSF) to found the French Section of the Workers' International.