The Roman provinces were the administrative regions of Ancient Rome outside Roman Italy that were controlled by the Romans under the Roman Republic and later the Roman Empire. Each province was ruled by a Roman appointed as governor.[better source needed]
For centuries, it was the largest administrative unit of the foreign possessions of ancient Rome. With the administrative reform initiated by Diocletian, it became a third level administrative subdivision of the Roman Empire, or rather a subdivision of the imperial dioceses (in turn subdivisions of the imperial prefectures).