Gallo (endonym: Galo; French: langue gallèse) is a regional language of eastern Brittany. It is one of the langues d'oïl, a Romance sub-family that includes French. Today it is spoken only by a minority of the population, as the standard form of French now predominates in this area.
Gallo was originally spoken in the Marches of Neustria, an area now corresponding to the border lands between Brittany, Normandy, and Maine. Gallo was a shared spoken language among many of those who took part in the Norman conquest of England, most of whom originated in Upper (i.e. eastern) Brittany and Lower (i.e. western) Normandy, and thus had its part, together with the much bigger role played by the Norman language, in the development of the Anglo-Norman variety of French which would have such a strong influence on English.