Leuci in the context of Belgica Prima

Gallia Belgica ("Belgic Gaul") was a province of the Roman Empire located in the north-eastern part of Roman Gaul, in what is today primarily northern France, Belgium, and Luxembourg, along with parts of the Netherlands and Germany.

Before the Roman province came into existence in about 50 BC, the region was conquered by Julius Caesar during his Gallic Wars. His report, the Commentarii de Bello Gallico, described Belgic Gaul as one of the three parts of Gaul (Tres Galliæ), the other two being Gallia Aquitania and Gallia Lugdunensis. Belgica stretched from the Marne and Seine rivers, which Caesar described as a cultural boundary between the Belgae and the Celtic Gauls. In the north and east it stretched all the way to the Rhine. The official Roman province of this name was later created by emperor Augustus in 22 BC, and named after the Belgae, as the largest tribal confederation in the area. However, it also included the territories of the Treveri, Mediomatrici, Leuci, Sequani, and others who Caesar did not explicitly designate as Belgic.