Legio I Armeniaca: one of the legions of the later Roman empire. Its name means "the Armenian legion".
This legion is mentioned in the late-antique text known as Notitia Dignitatum. It must first have been the garrison of one of the two provinces of Armenia, and must have become part of the Roman field army later. This was a more prestigious position.
The legion was probably founded in the third century, but we do not know by whom. It took part in the ill-fated Persian campaign of the emperor Julian the Apostate (363).