The Menapii were a Belgic tribe dwelling near the North Sea, around present-day Cassel, during the Iron Age and the Roman period.

The Belgae were a large confederation of tribes living in northern Gaul, between the English Channel, the west bank of the Rhine, and the northern bank of the river Seine, from at least the third century BC. They were discussed in depth by Julius Caesar in his account of his wars in Gaul. Some peoples in southern Britain were also called Belgae and had apparently moved from the continent. T. F. O'Rahilly believed that some had moved further west and he equated them with the Fir Bolg in Ireland. The Roman province of Gallia Belgica was named after the continental Belgae. The term continued to be used in the region until the present day and is reflected in the name of the modern country of Belgium.