René Blum (13 March 1878 – September 1942) was a French Jewish theatrical impresario. He was the founder of the Ballet de l'Opéra at Monte Carlo and was the younger brother of the Socialist Prime Minister of France, Léon Blum. A Jew, he was interned in various camps from 1941 until his death at the Auschwitz concentration camp in late September 1942. While imprisoned in the camps, he was known for keeping up the spirits of his fellow prisoners with tales of his life in the arts. Blum contributed to the catalogue of the 1912 Salon de la Section d'Or, an early Cubist exhibition in Paris. He became a friend of Marcel Proust, and it was on his advice that Proust turned to Bernard Grasset to publish Du côté de chez Swann. where Sergei Diaghilev's Ballets Russes was based. In 1938, their new company was allowed to regain the name Ballet Russe de Monte-Carlo (although the company fled for the United States in 1939, and was thereafter mostly based in New York City). He was murdered by the Nazis at age 64 in late September 1942.