There are approximately 3000 castles, farm-castles, citadels, manors or palaces in Belgium. Belgium has one of the highest density of castles per square km in the world, if not simply the highest. Some regions (eg. the Condroz, Hesbaye, Brabant...) have an average two castles per village. Belgium has over 400 castles that are open to the public, either for sightseeing, receptions, seminars, events or as hotels, restaurants or holiday centres.
The French word for castle is 'château', be it for an old medieval fortress ('château-fort') or a residential castle. The term 'château-ferme' means that a medieval castle has been transformed into a farm nowadays, or acted as both castle and farm in the Middles Ages. The province of Namur, Liege and Luxembourg have the most interesting medieval fortresses and citadels, thanks ro the rugged landscape of the Meuse valley and the Ardennes forest, and the abundance of bluestones in the former and yellow granite in the latter. The provinces of Namur and Liege have by far the highest density of castles and probably the most diversified in styles and most attractive ones too. The province of Hainaut also has lots of 'châteaux' in a style halfway between the rest of Wallonia and those of Flanders.
In Dutch-speaking Flanders, castles are called "kasteel" or "hof" ('court', like in "Hampton Court"). Flemish castles are typically made of brick due to the lack of stones in this flat region. Castles tend to be newer in average too, mostly 18th or 19th century.
Here is a list by province. The number in brackets indicates how many castles are listed on this site. Note that the original names in French or Dutch are mentioned in the listing below. There are 961 castles listed so far.
NB : Castles with a detailed page on Eupedia are listed here by historical period.