Terminal High Altitude Area Defense (THAAD), formerly Theater High Altitude Area Defense, is an American anti-ballistic missile defense system designed to shoot down short, medium, and intermediate-range ballistic missiles in their terminal phase by intercepting with a hit-to-kill approach. THAAD was developed after the experience of Iraq's Scud missile attacks during the Gulf War in 1991. The THAAD interceptor carries no warhead, instead relying on its kinetic energy of impact to destroy the incoming missile.

An anti-ballistic missile (ABM) is a surface-to-air missile designed to counter ballistic missiles. Ballistic missiles are used to deliver nuclear, chemical, biological, or conventional warheads in a ballistic flight trajectory. The term "anti-ballistic missile" is a generic term for a system designed to intercept and destroy any type of ballistic threat; however, it is commonly used for systems specifically designed to counter intercontinental ballistic missiles (ICBMs).