Legio III Augusta was a Roman legion levied by Augustus in 43 BC. Activity of this legion in the African Roman provinces, its principal theatre of operations, is still mentioned in late 4th century, early 5th century. Among the emblems of the legion were the winged horse Pegasus and the Capricorn.
The III Augusta was probably present in the Battle of Philippi in 42 BC, where Augustus and Marcus Antonius defeated the army of the senators that conspired to murder Julius Caesar. After this victory, the III Augusta stayed under the command of Augustus, probably in Sicily, where Sextus Pompeius, son of Pompey had started a rebellion.
From 30 BC onwards, Legio III Augusta was stationed in the province of Africa. The legion was involved mainly in construction activities. Although Africa was a traditional peaceful part of the Empire, between 17 and 24 AD, they were involved in the war against the mutinous Numidian and Mauritanian tribes. In 18 AD, a subunit was destroyed in a guerrilla attack. This disaster was probably due to coward behaviour, because afterwards, the all legion was punished by decimation, that is, the killing of every tenth legionary. This procedure was the most serious action a commander could impose on his soldiers and rarely used. After that, Legio VIII Hispana was sent to reinforce Africa and by 24 AD the rebellion was over.
In the 1st century AD, Africa was the only province controlled by a senator, the proconsul governor. Thus, it was important for the Emperor that this man, also commander of III Augusta, would be loyal. Sulpicius Galba, emperor in the Year of the four emperors occupied the position between 45 and 46 AD.
In the last years of the reign of Nero, Lucius Clodius Macer, proconsul of Africa, revolted and levied another legion, I Macriana Liberatrix to join forces with III Augusta. In the confusing year of 69 AD, both legions supported first Galba, then Vitellius and finally Vespasian, although took no part in the battles in Italy.
In 75 AD, Vespasian moved the campo of III Augusta from Ammaedara to Theveste. In the reign of Hadrian (117-138), the legion was stationed at Lambaesis in Numidia. The legion was to stay there for the next two centuries, guarding the province from the Berber tribes. Men from the III Augusta were occasionally used in several campaigns against Parthia. It is know also the presence of legionaries from this African legion in the Marcomannic campaign of Marcus Aurelius against the Hungarians.
3rd century AD was a time of crisis for the III Augusta. First, they suffered heavy losses in a war against a desert tribe, having to receive reinforcements from the recently disbanded Legio III Gallica. In 238 AD, the Year of the seven emperors, the legion suppressed the revolt of Gordian I and Gordian II, but was disbanded by their successor Gordian III.
In 252 AD, Valerian I reconstituted the III Augusta and gave them the cognomen of Iterum Pia Iterum Vindex (Again faithful, again avenger). The purpose of this reconstitution was to wage a war against a federation of Berber tribes that threatened the empire. This war was over in 260 AD but between 289-297, the situation was once more out of hand and emperor Maximianus went to Africa to command the Numidian legions personally. Their presence in Africa appears in the sources until late 4th century, early 5th century.