Joseph Déjacque (December 27, 1821, Paris – 1864, Paris) was a French early anarcho-communist poet and writer. Déjacque was the first recorded person to employ the term libertarian (French: libertaire) for himself in a political sense, in a letter written in 1857 criticizing Pierre-Joseph Proudhon for his sexist views on women, his support of individual ownership of the product of labor, and of a market economy, saying: "it is not the product of his or her labor that the worker has a right to, but to the satisfaction of his or her needs, whatever may be their nature."

Of unknown origins, Déjacque was first heard of when arrested as part of the revolutionary upheavals in France in 1848. Imprisoned for a time for socialist agitation, he was released but rearrested in 1851, and was sentenced to two years of prison for his collection of poems Les Lazaréennes, Fables et Poésies Sociales, with an additional penalty of 2000 francs. He escaped to London around the time of the December 2, 1851 coup d'état. While in Jersey between 1852 and 1853 he published "La question révolutionnaire", an exposition of anarchism. From there he went to the USA where he spoke to workers associations in New York and was a signatory to the programme of the First International there in 1855.^{[citation needed]}