A stunner is a type of non-lethal weapon, a type of directed energy weapon designed to temporarily shock the nervous system of a lifeform and cause a loss of consciousness. These weapons are typically used by police to subdue detainees in many civilizations. The nomenclature "stunner" specifies a device that is locked to operate on a non-lethal energy cycle, without the capability to increase power to a "kill" setting, although many can be misused in lethal applications. For example, a phaser stun can kill a humanoid if applied to the brain at close range.

Many stunner applications exist as hand-held weapons, with some emitting beams or arcs of energy like a stun pistol, arrestor or knock-out ray; while others can be used in physical contact as mêlée weapons, such as a shock prod. Some stunner variations can be used as projectile weapons, the stun grenade for example.