Mauretania Caesariensis was a Roman province located in northwestern Africa. It was the easternmost of the North African Roman provinces, in present Algeria, with its capital at Caesarea (hence the name Caesariensis; one of many cities simply named after the imperial cognomen that had become a title), now Cherchell.
Historical background 
In the first century AD, Roman Emperor Claudius divided the westernmost Roman province in Africa, named Mauretania (land of the people of the Mauri, hence the word Moors), into Mauretania Caesariensis and Mauretania Tingitana.
At the time of Diocletian and Constantine the Great, both provinces were assigned to the administrative Diocese of Africa, in the praetorian prefecture of Italy, while Tingitana was an outpost of the Diocese of Spain. Caesarea was a major center of Jewry before 330, Sitifis one of the centres of the soldier cult of Mithras. Christianity was spread throughout in the 4th and 5th century.
Under Diocletian's Tetrarchy reform, the easternmost part was broken off as a tiny separate province, Sitifensis, called after its inland capital Sitifis (Sétif) with a significant port at Saldae (presently Béjaïa).
Among the ruling class, Trinitarian Christianity was replaced by Arianism under the Germanic kingdom of the Vandals, which was established in 430, when the Vandals crossed the Strait of Gibraltar. The Vandal kingdom was extinguished by the Byzantine armies circa 533, but most of Mauretania Caesariensis remained under the control of local Moorish rulers such as Mastigas, and it was not until the 560s and 570s that Byzantine control was established in the interior. The Byzantine Exarchate of Africa was in its turn overrun by the Muslim caliphate under the Umayyad dynasty, ending Late Antique Roman culture there; most of former Mauretania Caesariensis became part of the westernmost Islamic province, henceforth called (al-)Maghrib.
The principal exports from Caesariensis were purple dyes and valuable woods; and the Amazigh or Mauri were highly regarded by the Romans as soldiers, especially light cavalry. They produced one of Trajan's best generals, Lusius Quietus, and the emperor Macrinus.
See also 
- Westermann, Großer Atlas zur Weltgschichte (in German)