Toulouse refounded by the Romans on the banks of the Garonne. Tolosa enters the historical period in the 2nd century BC, when it became a Roman military outpost. After the conquest of Gaul, it was developed as a Roman city in Gallia Narbonensis.

Under the reign of Emperor Augustus and thanks to the Pax Romana, the Romans moved the city a few kilometres from the hills where it was an oppidum to the banks of the Garonne, which were more suitable for trade.

In the second half of the 1st century, the emperor Domitian distinguished Toulouse by placing it under the patronage of the goddess Pallas Athena, so that the Latin poets Martial, Ausonius and Sidonius Apollinaris called the city Palladia Tolosa (Palladian Toulouse), a term that was still used in the Renaissance and even today when the city is presented as propitious to the arts and sciences.

Around the year 250, Toulouse was marked by the martyrdom of Saturnin, the first bishop of Toulouse. This episode illustrates the difficult beginnings of Christianity in Roman Gaul.

In the 5th century, Toulouse fell to the Visigothic kingdom and became one of its major cities, even serving as its capital, before it fell to the Franks under Clovis in 507 (Battle of Vouillé). From that time, Toulouse was the capital of Aquitaine within the Frankish realm.

In 721, Duke Odo of Aquitaine defeated an invading Umayyad Muslim army at the Battle of Toulouse. Many Arab chroniclers consider that Odo’s victory was the real stop to Muslim expansion into Christian Europe, incursions of the following years being simple raids without real will of conquest since they did not besiege the cities (including the one that ended with Charles Martel’s victory at the Battle of Tours, also called the Battle of Poitiers).

The Frankish conquest of Septimania followed in the 750s, and a quasi-independent County of Toulouse emerged within the Carolingian sub-kingdom of Aquitaine by the late 8th century.