Genevoise sauce is a type of French brown sauce made from fish fumet, mirepoix, red wine, and butter usually accompanied with fatty fishes such as trout and salmon. There are versions of this sauce made with white wine.
The sauce was originally made from the braising liquid from dishes prepared "à la genevoise". One of the first recipes for the sauce was given by chef Louis Eustache Ude who used white wine instead of red wine.
This sauce was later further popularized by the French chef, Auguste Escoffier in his book Le guide culinaire.