Casteau (Walloon: Castea) originated as a village in the Hainaut province of Wallonia, in the French speaking south of Belgium.
The village is located between the towns of Mons and Soignies on the Mons-Brussels road.
The name Casteau is the French word for castle, and stems from the Latin castellum.
The northwestern part of the village is a plain with dispersed houses and farms with typical hedges.
Around the village, there are several woods (comprising oaks, beeches, chestnuts, and poplars), fields (growing potatoes, sugar beets, corn, and wheat), and prairies (for cows and horses).