European Union–NATO relations

The European Union (EU) and the North Atlantic Treaty Organisation (NATO) are two main treaty-based Western organisations for cooperation between member states, both headquartered in Brussels, Belgium. Their natures are different and they operate in different spheres: NATO is a purely intergovernmental organisation functioning as a military alliance, which serves to implement article 5 of the North Atlantic Treaty on collective territorial defence.

Source: Wikipedia — European Union–NATO relations (CC BY-SA 4.0)