Gallia Narbonensis was created in 121.

Four: Gallia Narbonensis, Gallia Aquitania, Gallia Lugdunensis, and Gallia Belgica

The ancient Romans referred to modern day France and Belgium as Gaul. Prior to the Roman conquest of the region, the Romans divided Gaul into five regions: Gallia Belgica (Belgium, the Netherlands, and Northern France), Gallia Celtica (Brittany and Central France), Gallia Cisalpina (Northern Italy), Gallia Narbonensis (Southeastern France), and Gallia Aquitania (Southwestern France).

There was not a Roman Empire of Gaul. Gaul was part of the Roman Empire as a whole and was subdivided into the Roman provinces of Gallia Narbonensis, Gallia Aquitania, Gallia Lugdunensis and Gallia Belgica. There was a short period when Britannia and Gallia formed a splinter empire. Historians call it Gallic Empire, but the Romans did not use this term. It was brought back into the fold by the emperor Aurelian 14 years later.

Gaul was invaded by the Vandals, Sueves and Alans who crossed the frozen river Rhine in 406.

Caesar conquered the rest of Gaul (France Belgium, Luxembourg, Holland south of the Rhine and Germany west of the Rhine) when he was governor of the Roman Province of Gallia Narbonensis (southern France). This area of Gaul was already under the Romans). The newly conquered Gaul became the Roman province of Gallia Comata. It was subdivided into three provinces by Augustus: Gallia Belgica (in the North), Gallia Lugdunensis (in the centre) and Gallia Aquitania (in the southwest). Later, the frontier areas along the river Rhine were separated from Gallia Belgica and the new provinces of Germania Inferior (the part now in Holland) and Germania Superior (the part now in Germany) were created.