Gallia Belgica (sometimes called Belgica Prima) was a Roman province. Different parts of it are in several countries today, including Belgium, the entire south of the Netherlands, a part of France between Paris, Belgium, the English Channel, and the Ardennes, and the Rhineland part of Germany, which is between the Rhine river in the east, and Belgium and the Netherlands in the west. In other words, it includes a large part of the part of Europe called the Low Countries.
The people who lived in Gallia Belgica were called the Belgae. They were a group of tribes within the bigger country called Gaul, which covered all of modern France. According to Julius Caesar, the Belgae were different. He said that the border between Belgica and the main Celtic part of Gaul was the Marne and the Seine rivers and that the border with Germania was the Rhine river. It is no longer certain what language or languages were spoken in Gallia Belgica, but historians know there was an influence of both Celtic and Germanic languages.
The area was conquered in 57 BC by Julius Caesar. Emperor Diocletian changed the Gaulish provinces around 300 AD. He split Belgica into two provinces: Belgica Prima and Belgica Secunda. Belgica Prima had Treveri (Trier) as its main city and was the eastern part. The border between Belgica Prima and Belgica Secunda was along the River Meuse.
In 406 AD, the Vandals, Burgundians and other tribes crossed the Rhine. They defeated the Gaulish forces. Belgica Secunda became in the 5th century the center of Clovis' Merovingian kingdom and during the 8th century the heart of the Carolingian Empire.