A hypersonic glide vehicle (HGV) is a type of warhead for ballistic missiles that can maneuver and glide at hypersonic speed. It is used in conjunction with ballistic missiles to significantly change their trajectories after launch. Conventional ballistic missiles follow a predictable ballistic trajectory and are vulnerable to interception by the latest anti-ballistic missile (ABM) systems. The in-flight maneuverability of HGVs makes them unpredictable, allowing them to effectively evade air defenses. , hypersonic glide vehicles are the subject of an arms race.
There have also been reports of other hypersonic glide vehicle being mounted on the other ballistic missiles.
Boost-glide weapons are generally designed to avoid existing missile defense systems, either by continually maneuvering or by flying at lower altitudes to reduce warning time. This generally makes such weapons easier to intercept using defensive systems intended for lower-altitude "low-tier" targets. Flying at lower speeds than short-range ballistic missile warheads makes them easier to attack. Those that approach with very low terminal attack profiles are even subject to attack by modern hypervelocity guns and railguns. The evasion capabilities that HGVs employ are largely limited to the upper atmospheric flight span.