The North Atlantic Treaty Organization/Organisation (NATO); Organisation du Traité de l'Atlantique de Nord (OTAN); (also called the North Atlantic Alliance, the Atlantic Alliance, or the Western Alliance) is a military alliance established by the signing of the North Atlantic Treaty on 4 April 1949. With headquarters in Brussels, Belgium, the organization established a system of collective defense whereby its member states agree to mutual defense in response to an attack by any external party.

.nato was an Internet top-level domain. The nato TLD was added in the late 1980s by the NIC for the use of NATO, who felt that none of the then existing TLDs adequately reflected their status as an international organization. Soon after this addition, however, the NIC created the .int TLD for the use of international organizations, and convinced NATO to use nato.int instead. However, the NATO TLD, although no longer used, was not deleted until July 1996.