Legio III Gallica was a Roman legion levied by Julius Caesar around 49 BC, for his civil war against the conservative republicans led by Pompey. The cognomen Gallica suggests that recruits were originally from the Gallic Roman provinces. The legion was still active in Egypt in the early 4th century. The legion's symbol was a bull.
The legion took part in all Julius Caesar's campaigns against his enemies, including the battles of Pharsalus and Munda. Following Caesar's death, the III Gallica was integrated in the army of Marcus Antonius, a member of the second triumvirate, for his campaigns against the Parthians. They were included in the army levied by Fulvia and Lucius Antonius (Antonius' wife and brother) to oppose Octavianus, but ended by surrendering in Peruggia, in the winter of 41 BC. After the battle of Actium and Antonius suicide, the III Gallica was sent again to the East, where they garrisoned the province of Syria.
The III Gallica was used in Gnaeus Domitius Corbulo campaign against the Parthians over the control of Armenia. Corbulo's successes triggered emperor Nero's paranoia of persecution and eventually the general was forced commit suicide. After this, III Gallica is transferred to Moesia province, in the Danube border.
In the year of the four emperors 69 AD, the legion, and the rest of the Danubian army, aligned first with Otho, then with Vespasian. They were instrumental in the final defeat of Vitellius in the battle of Cremona and in the accession of the Flavians to the throne of Rome.
After this civil war, the legion was again sent to Syria, were they fought against the Judea rebellions of the 2nd century. They also took part on Lucius Verus' (161-166 AD) and Septimius Severus (197-198 AD) campaigns against the Parthian empire, none with noteworthy success.
In 219, the legion was disbanded by emperor Heliogabalus, after an unsuccessful rebellion of its commander. The legionaries were transferred namely to Legio III Augusta, stationed in the Africa provinces. However, the following emperor, Alexander Severus, reconstituted the legion and redeployed them back in Syria.
The III Gallica records them become obscure. Little is known about the legion's whereabouts, but, in 323, they were still in Syria.
See also: List of Roman legions