The Legio III Parthica was a Roman legion created by Emperor Septimius Severus in 197 for his campaign against the Parthian Empire. This legion remained active in the eastern provinces until the beginning of the 5th century. Its emblem was a bull.
With its two sister legions, I Parthica and II Parthica, the third was raised in the same context. The campaign was successful and Ctesiphon, the Parthian capital, was taken and sacked. The III Parthica remained in the area, guarding the new province of Mesopotamia. The legion was headed by a prefect from the equestrian order. His main camp was at Rhesaena, with the task of keeping the main roads safe and protecting the province against the Parthians. During the 3rd century, the III Parthica took part in several campaigns launched against the Parthians and then against the Sassanids. At the beginning of the 5th century, she was stationed at Apadna near the confluence of the Chaboras and the Euphrates.