Guesde, Jules, 1845-1922, French socialist, whose original name was Basile. Exiled for his support of the Paris commune, he became a confirmed Marxist after 1876 and, with Paul Lafargue, led in advocating socialism in France and a policy of noncompromise with the existing government. Guesde was largely responsible for the formation (1905) of the unified Parti socialiste, which marked the triumph of Marxism over variant forms of French organized socialism. He was a deputy (1893-1921) and served in the cabinet during World War I, when his patriotism overcame his former uncompromising stand. He wrote many socialist pamphlets and articles.