The city of Brussels (in Dutch: Stad Brussel) is one of the 19 municipalities (the largest) making the Region of Brussels-Capital. Even if some people mix the capital of Belgium with Brussels, Belgium institutions (Art 194 et 166) state clearely that the capital of Belgium is Brussels in its widest interpretation, meaning the Region. In practice, administration institutions are indeed located in the city of Brussels, but also in the other 18 areas part of the Region of Brussels-Capital.

As similar to the other municipalities, the city of Brussels is lead by a mayor, that is not the same as the Minister-President of the Region, nor the governor of the Region.

The Region of Brussels-Capital (in Dutch Brussels Hoofdstedelijk Gewest) is one of the three regions that make up Belgium. Inhabitants of Brussels are either part of the Flemish community or the French speaking community, or one of the other nationalities of the European Union in the city. The Brussels-Capital Region is officially bilingual, while the majority of its residents speak French.

According to the way the federalism works in Belgium, Brussels institutions may look a bit complex. We can distinguish:

• 19 municipalities
• 6 zones of inter-municipalities police
• 1 administration at the region level
• 2 specific communities Flemish (VGC or Vlaamse Gemeenschaps Commissie with a simple rule making power) and wallons (COCOF or Commission communautaire française with a power of law and rule maker).
• 1 bi-community authority: CCC-GGC (Commission Communautaire Commune-Gemeenschapelijke GemeenschapsCommissie), being the joint-venture of VGC and COCOF.

Culture, education and public services links to the community are in charge of each community.

The city is often considered as the (non-official) capital of the European Union because it hosts two of the four main institutions. The European Commission and the European Union Council have their headquarters in Brussels (the first one is in the Berlaymont building and the Council is in the Justus Lipsius building facing it). The European Parliament is in Brussels for the ordinary sessions and the commissions, in Strasbourg for the ordinary sessions and its administrative headquarters are in Luxembourg.

Brussels is the Head Quarter of NATO (North Atlantic Treaty Organisation).