Unemployed :

La Loge (gratis)
Belgian Museum of Freemasonry 
BELvue Museum
Brussels Museum of Mill and Food 
Centre for Fine Arts (BOZAR)
Cinquantenaire Museum (Royal Museums of Art and History) 
Coudenberg-Voormalig Paleis van Brussel 
Ixelles Museum (gratuit)
Le Botanique 
Magritte Museum (Belgian Museums of Fine Arts) (gratuit)
Museum of Ancient Art (Royal Museums of Fine Arts of Belgium) (gratuit)
Museum of Musical Instruments (mim) 
Museums of the Far East (Royal Museums of Art and History) 
Palace of Charles de Lorraine (Belgian Royal Library) 
Porte de Hal (Royal Museums of Art and History) 
Royal Museum of Central Africa 
Wiels - Center for Contemporary Art 

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art & marges museum
Belgian Museum of Freemasonry
BELvue Museum
Bibliotheca Wittockiana - Museum of Book Bindings and Book Arts
Brussels Museum of Industry and Labour - La Fonderie
Coudenberg-Voormalig Paleis van Brussel
Museum of Costume & Lace (Museums of the City of Brussels)
Museum of the City of Brussels (Maison du Roi / Museums of the City of Brussels)
Royal Museum of Central Africa
Wiels - Center for Contemporary Art

* This list is not exhaustive, most of the museums also offer other discounts (students, seniors, etc ...)