(After J.B. Bury.) This is intended primarily to provide a quick reference for the divisions of the geographical administration of the Empire in Late Antiquity after the reforms of Diocletian.
- The one Roman Empire
- The Empire was divided into the two domains of the Augusti: the East and West (partes orientis et occidentis)
- The two halves of the Empire were further divided into the four Praetorian Prefectures: Illyricum, the East (in pars orientis); the Gauls, Italy (in pars occidentis)
- The four Prefectures were further divided into the fourteen Dioceses: in the Gauls: Britain, Gaul, Viennensis (Southern Gaul), Spain; in Italy: Africa, the Italies (the Vicarius urbis Romae and the Vicarius Italiae), Illyricum; in Illyricum: Dacia, Macedonia; in the East: Thrace, Asiana, Pontus, Oriens, Egypt
- The fourteen Dioceses were further divided into the Provinces. The number of Provinces was variable in the Late Empire. For convenience, we may use the number of about 100 in the year 314 as given in the Oxford Classical Dictionary, s.v. Diocletian.