The gun turret is a location from which weapons can be fired that affords protection, visibilty, and some cone of fire. Medevial fortifications introduced the gun turret. A modern gun turret more often is a weapon mount that houses the crew or mechanism of a projectile-firing weapon and at the same time lets the weapon be aimed and fired in some degree of azimuth and elevation (cone of fire). The modern turret often increases azimuth by means of a rotating weapon platform. A turret can be mounted on a fortified building or structure such as a a coastal blockhouse land battery, or on a combat vehicle, a naval ship, or a military aircraft.

Turrets may be armed with one or more machine guns, automatic cannons, large-calibre guns, or missile launchers. It may be manned or remotely controlled, and is often armoured.

A small turret, or sub-turret on a larger one, is called a cupola. The term cupola is also used for a rotating turret that carries a sighting device rather than weaponry, such as that used by a tank commander. A finial is an extremely small sub-turret or sub-sub-turret mounted on a cupola turret.