As of 2021, how many countries are there in the North Atlantic Treaty Organization (NATO)?

The North Atlantic Treaty Organization (NATO), also called the North Atlantic Alliance, is an intergovernmental military alliance between 28 European countries and 2 North American countries. The organization implements the North Atlantic Treaty that was signed on 4 April 1949.

NATO constitutes a system of collective security, whereby its independent member states agree to mutual defense in response to an attack by any external party. The NATO headquarters are located in Brussels, Belgium, while the headquarters of Allied Command Operations is near Mons, Belgium.

Since its founding, the admission of new member states has increased the alliance from the original 12 countries to 30. The most recent member state to be added to NATO was North Macedonia on 27 March 2020. NATO currently recognizes Bosnia and Herzegovina, Georgia, and Ukraine as aspiring members. An additional 20 countries participate in NATO's Partnership for Peace programme, with 15 other countries involved in institutionalized dialogue programmes.