It is limited to the east by the Archdiocese of Algiers, to the south by the Diocese of Laghouat, to the west by the border of Morocco; it covers nearly 56,000 km2 (22,000 sq mi).

It is believed that its current population is around 9.8 million inhabitants spread over 9 departments, of which 1,500 are Catholic.

At the time of Saint Augustine, about thirty bishoprics existed on the current extent of the diocese; from the 16th to the 18th centuries.

After the massive departure of the French at the independence of Algeria in 1962, then of foreign workers at the beginning of the Algerian Civil War, the Catholic community only has a few hundred members nowadays.

[1] Pierre Claverie, bishop of Oran between 1981-1996, was murdered together with a Muslim assistant by a bomb that had been planted at the door of the bishopric.