Louis Gustave Fortuné Ratisbonne (29 July 1827 – 24 September 1900) was a French man of letters. He was born at Strasbourg. He was the son of the banker Adolphe Ratisbonne and his wife Charlotte Oppenheim (daughter of Salomon Oppenheim), and the nephew of the priests Marie Theodor Ratisbonne and Marie-Alphonse Ratisbonne. He studied at the school of his native town and at the College Henry IV in Paris. He was connected with the Journal des Debats from 1853 to 1876; became librarian of the palace of Fontainebleau in 1871, and three years later to the Senate.