Numidia (Greek Nomadia, "land of Nomads"), in ancient geography, was a territory of north Africa between Mauretania on the W. and the Roman province of Africa on the E., corresponding roughly to the modern Algiers. Numidia became a formidable antagonist of Rome under Jugurtha (q.v.) and Juba I. ; after the defeat of the latter in 46 B.C. it was formed into a Roman province. "When Juba II. was made King of Mauretania by Augustus, western Numidia was incorporated in his dominions, and the name was henceforward confined to the east part of the former province.