The North Atlantic Treaty Organization (NATO) NATO's headquarters are located in Haren, Brussels, Belgium, one of the 28 member states across North America and Europe, the newest of which, Albania and Croatia, joined in April 2009
NATO has twenty-eight members, mainly in Europe and North America. Some of these countries also have territory on multiple continents, which can be covered only as far south as the Tropic of Cancer in the Atlantic Ocean, which defines NATO's "area of responsibility" under Article 6 of the North Atlantic Treaty
For more: https://en.wikipedia.org/wiki/NATO