The Air Defense Artillery Branch is the air defense branch of the United States Army, specializing in the use of anti-aircraft weapons to conduct anti-aircraft warfare operations. In the U.S. Army, these groups are composed of mainly air defense systems such as the Patriot Missile System, Terminal High Altitude Area Defense (THAAD), and the Avenger Air Defense system which fires the FIM-92 Stinger missile.

Anti-aircraft warfare is the counter to aerial warfare and it includes "all measures designed to nullify or reduce the effectiveness of hostile air action". It includes surface based, subsurface, and air-based weapon systems, associated sensor systems, command and control arrangements, and passive measures. It may be used to protect naval, ground, and air forces in any location. However, for most countries, the main effort has tended to be homeland defence. Missile defence is an extension of air defence, as are initiatives to adapt air defence to the task of intercepting any projectile in flight.