Léonce Rosenberg (12 September 1879, Paris – 31 July 1947, Neuilly-sur Seine), was an art historian, art collector, publisher and one of the most influential French art dealers of the 20th century. The son of an antique dealer Alexander Rosenberg and brother of the gallery owner Paul Rosenberg (21 rue de la Boétie, Paris), Léonce, a prominent gallery owner in Paris at the end of World War I, would become one of the world's major dealers of Modern art.