Walloon Flanders (Dutch: Waals Vlaanderen, French: Flandre wallonne) was a semi-independent part of the County of Flanders, composed of the burgraviates of Lille, Douai and Orchies. It is sometimes referred to as Lille-Douai-Orchies.
Walloon Flanders was part of the County of Flanders from the early Middle Ages, but was ceded to the Kingdom of France from 1304 to 1369, by the Treaty of Athis-sur-Orge which concluded the Franco-Flemish War (1297-1305). As a result it was to some degree institutionally distinct from the County of Flanders and in some lists it even features as one of the Seventeen Provinces. Furthermore, Walloon Flanders adhered to the Union of Arras in 1579, whereas the County of Flanders joined the Union of Utrecht.
In 1678, Walloon Flanders was annexed to France after the Treaties of Nijmegen.
Together with Maritime Flanders (Westhoek), it forms French Flanders, and is today the part of the Departement du Nord roughly corresponding with the Arrondissement of Lille and the Arrondissement of Douai.