These are the main rivers of Belgium.

By basin

Meuse 936km  
Grevelingen, Krammer, Volkerak (branches in the Netherlands)
Dintel (in Dintelsas, Netherlands) 
Mark (near Oudenbosch, Netherlands)
Aa or Weerijs (in Breda, Netherlands)
Meuse (Dutch: Maas) (main branch at Stellendam, Netherlands) 
Dieze (in 's-Hertogenbosch, Netherlands)
Dommel (in 's-Hertogenbosch, Netherlands)
Rur (Dutch: Roer) (in Roermond, Netherlands)
Inde (in Jülich, Germany)
Geul (French: Gueule, German: Göhl) (near Meerssen, Netherlands)
Jeker (French: Geer) (in Maastricht, Netherlands)
Voer (French: Fouron) (in Eijsden, Netherlands)
Berwinne (Dutch: Berwijn) (near Visé)
Ourthe (in Liège)
Vesdre (German: Weser)  (near Liège)
Hoëgne (in Pepinster)
Gileppe (in Limbourg)
Amblève (German: Amel) (in Comblain-au-Pont)
Salm (in Trois-Ponts)
Eau Rouge (near Stavelot)
Warche (near Malmedy)                              
Hoyoux (in Huy)
Mehaigne (in Huy)
Sambre (in Namur)
Bocq (in Yvoir)
Molignée (in Anhée)
Lesse (in Dinant-Anseremme)
Viroin (in Vireux-Molhain, France)
Semois (in Monthermé, France)
Rulles (near Tintigny)
Mellier (near Marbehan)
Mandebras (near Rulles)
Chiers (in Bazeilles, France)

Rhine
Rhine (main branch at Hoek van Holland, Netherlands) 
Moselle (in Koblenz, Germany)
Sauer (French: Sûre) (in Wasserbillig, Luxembourg)
Our (in Wallendorf, Germany)
Alzette (in Ettelbrück, Luxembourg)
Attert (in Colmar-Berg, Luxembourg)

Scheldt  
Scheldt (Dutch: Schelde, French: Escaut) (near Flushing, Netherlands) 
Rupel (in Rupelmonde)
Nete (in Rumst)
Kleine Nete (in Lier)
Aa (in Grobbendonk)
Wamp (in Kasterlee) 
Grote Nete (in Lier)
Wimp (in Herenthout)
Molse Nete (in Geel)
Laak (in Westerlo)
Dijle (French: Dyle) (in Rumst)
Zenne (French: Senne) (near Mechelen)
Maalbeek (in Grimbergen)
Woluwe (in Vilvoorde)
Kleine Maalbeek (in Kraainem)
Maalbeek (French: Maelbeek) (in Schaerbeek)
Molenbeek (in Brussels-Laken)
Neerpedebeek (in Anderlecht-Neerpede)
Zuun (in Sint-Pieters-Leeuw-Zuun)
Geleytsbeek (in Drogenbos)
Linkebeek (in Drogenbos)
Molenbeek (in Lot)
Senette (in Tubize)
Hain (in Tubize)
Samme (in Braine-le-Comte-Ronquières)
Thines (in Nivelles)
Demer (near Rotselaar)
Velp (in Halen)
Gete (in Halen)
Grote Gete (in Zoutleeuw)
Kleine Gete (in Zoutleeuw)
Herk (in Herk-de-Stad)
Voer (in Leuven)
IJse (in Huldenberg-Neerijse)
Nethen (in Grez-Doiceau-Nethen)
Laan (in Huldenberg-Terlanen-Sint-Agatha-Rode)
Zilverbeek (in Rixensart-Genval)
Thyle (in Court-Saint-Étienne)
Orne (in Court-Saint-Étienne)
Houssière (in Mont-Saint-Guibert)
Durme (near Temse)
Dender (French: Dendre) (in Dendermonde)
Mark (French: Marcq) (in Lessines)
Ruisseau d'Ancre (in Lessines)
Zulle (in Ath)
Oostelijke Dender (in Ath)
Westelijke Dender (in Ath)
Lys (Dutch: Leie) (in Ghent)
Mandel (in Wielsbeke)
Gaverbeek (in Kortrijk)
Douve (in Comines-Warneton)
Rooigembeek (in Gavere)
Zwalm (in Zwalm)
Rone (in Kluisbergen)
Rhosne (in Ronse)
Haine (in Condé-sur-l'Escaut, France)
Hogneau (in Condé-sur-l'Escaut)
Honelle (in Quiévrain)
Aunelle (..)
Grande Honelle (..)
Petite Honelle (..)
Trouille (in Mons)
Obrecheuil (near Mons)

Seine 
 Seine (entering the English Channel in an estuary between Le Havre and Honfleur)
 Oise (near Paris, France)

Yser 
Yser  (Dutch: IJzer) (in Nieuwpoort)
 Ieperlee (in Diksmuide)

 
Belgium
Belgium