Mesarfelta was a Roman–Berber town in the province of Numidia. It was also a bishopric that is included in the Catholic Church's list of titular sees.^[1]

The historic Mesarfelta is believed to be what are now the ruins of El-Outaïa or those of Tolga, Henchir-El-Ksar,^[1] or may be Qastilya in Algeria^[2] (according to "Three North-African Topographical Notes (Islamic-Roman)").

The city is believed to have been constructed as a fortification by the Romans (with annexed "vicus"), in the second half of the first century near the Aures Mountains. It had an amphitheatre during Hadrians reign.^[3]

A barrier called Fossatum Africae, which marked the frontier between the territory of the Roman Empire and other lands, ran through Mesarfelta.^[4]

The city disappeared after the Muslim conquest in the second half of the 7th century.

The city of Mesarfelta was the seat of an ancient bishopric^[5] There are two Mesarfelta bishops historically remembered both in the Council of Carthage (411).

• "Lucianus"(Catholic) and "Bennatus"(Donatist).

• William Edward McManus 1967–1976
• Louis-Albert Vachon 1977–1981
• Basile Tapsoba 1981–1984
• Joseph Paul Pierre Morissette 1987–1990
• Michael Angelo Saltarelli^[7] 1990–1995
• Antonio Menegazzo, M.C.C.I. 1995-2019

• Mauretania Caesariensis
• Caesarea
• Thamugadi
• Lambaesis

• J. Baradez (1949). Gemellae. Un camp d'Hadrien et une ville aux confins sahariens aujourd’hui ensevelis sous les sables. Revue Africaine v. 93 p. 1-24.
• P. Trousset (2002). Les limites sud de la réoccupation Byzantine. Antiquité Tardive v. 10, p. 143-150.