A close-in weapon system (CIWS SEE-wiz) is a point-defense weapon system for detecting and destroying short-range incoming missiles and enemy aircraft which have penetrated the outer defenses, typically mounted on a naval ship. Nearly all classes of larger modern warships are equipped with some kind of CIWS device.

There are two types of CIWS systems. A gun-based CIWS usually consists of a combination of radars, computers, and rapid-firing multiple-barrel rotary cannons placed on a rotating turret. Missile-based CIWSs use either infra-red, passive radar/ESM, or semi-active radar terminal guidance to guide missiles to the targeted enemy aircraft or other threats. In some cases, CIWS are used on land to protect military bases. In this case, the CIWS can also protect the base from shell and rocket fire.