Paul Lafargue (January 15, 1842 – November 26, 1911) was a French revolutionary Marxist socialist journalist, literary critic, political writer and activist; he was Karl Marx's son-in-law, having married his second daughter Laura. His best known work is The Right to Be Lazy. Born in Cuba to French and Creole parents, Lafargue spent most of his life in France, with periods in England and Spain. At the age of 69, he and Laura died together in a suicide pact.
Lafargue was the subject of a famous quotation by Karl Marx. Shortly before Marx died in 1883, he wrote a letter to Lafargue and the French Workers' Party leader Jules Guesde, both of whom already claimed to represent "Marxist" principles. Marx accused them of "revolutionary phrase-mongering" and of denying the value of reformist struggles. This exchange is the source of Marx's remark, reported by Friedrich Engels: "ce qu'il y a de certain c'est que moi, je ne suis pas Marxiste" ("what is certain is that [if they are Marxists, then] I myself am not a Marxist").