- a medieval country in W Europe, extending along the North Sea from the Strait of Dover to the Scheldt River: the corresponding modern regions include the provinces of East Flanders and West Flanders in W Belgium, and the adjacent parts of N France and SW Netherlands.
- a powerful medieval principality in the SW part of the Low Countries, now in the Belgian provinces of East and West Flanders, the Netherlands province of Zeeland, and the French department of the Nord; scene of battles in many wars
