Flanders (Du., Vlaanderen) is the Dutch-language region and community of Belgium surrounding the Brussels Capital Region. It includes Flemish Brabant (Du., Vlaams Brabant), the portion of the former province of Brabant lying to the north of the language border drawn in 1962, that was set up as a separate province in conjunction with federalization.
During the Middle Ages, Flanders, roughly contiguous to the modern provinces of East and West Flanders, was an independent county and fief of France that constituted an alternating rival and ally of Brabant. Both Flanders and Brabant became integral parts of the southern Netherlands, beginning with the Burgundian regime.
Historical Dictionary of Brussels. Paul F. State.