Espagnole sauce is a basic brown sauce, and is one of Auguste Escoffier's five mother sauces of classic French cooking. Escoffier popularized the recipe, and his version is still followed today.
Espagnole has a strong taste, and is rarely used directly on food. As a mother sauce, it serves as the starting point for many derivatives, such as sauce africaine, sauce bigarade, sauce bourguignonne, sauce aux champignons, sauce charcutière, sauce chasseur, sauce chevreuil, and demi-glace. Hundreds of other derivatives are in the classical French repertoire.
Escoffier included a recipe for a Lenten espagnole sauce, using fish stock and mushrooms, in Le Guide culinaire, but doubted its necessity.