The Legio III Cyrenaica (Third Cyrenaic Legion) is a Roman legion formed during the Imperial era in the 1st century AD. It was originally stationed in Egypt, near Alexandria, and commanded by a prefect of a legion belonging to the equestrian order. His tutelary deity was the god Ammon-Zeus or Jupiter Hammon (a Jupiter wearing ram's horns), a traditional deity of Cyrenaica and the oasis of Ammon (Siwa, Egypt).
In 106 or 107, under the command of Caius Claudius Severus, it was partially or totally transferred to Petra, then to Bosra, to defend the new province of Arabia. His permanent camp was established north of the city of Bosra, capital of the province.
In Arabia, commanded by a propraetor legate belonging to the senatorial order, the III Cyrenaic legion sent detachments to patrol the whole province, and on the tracks of the desert. Traces of these detachments can be found as far south as Hegra or al-Jowf in Saudi Arabia. Detachments of this legion also took part in certain campaigns in Mesopotamia, such as the Parthian war of Trajan (115-117).
This legion, probably reduced in strength, remained in Bosra in the 4th and 5th centuries, reinforced from the reign of Diocletian by a new legion, the legio IV Martia, based in Lejjun.