Legio XXII Deiotariana was levied in 48 BC by Deiotarius the king of the Galatians, client of Rome.

After the accession of Augustus to the throne, XXII Deiotariana was allocated to Alexandria in Egypt, where it shared camp with Legio III Cyrenaica at least until 119. Its main tasks were to keep peace among the several ethnicities that lived in the country and suppress attacks from the desert tribes to the south.

During the civil war in the year of the four emperors, XXII Deiotariana supported Vespasian, who would eventually become the sole victor.

After 119, there are no more records from this legion, and it was presumably destroyed during the Jewish rebellion of 132-136

See also: List of Roman legions, Roman legion