A grenade launcher is a weapon that fires a specially designed, large-caliber projectile, often with an explosive, smoke, or gas warhead. Today, the term generally refers to a class of dedicated firearms firing unitary grenade cartridges. The most common type are man-portable, shoulder-fired weapons issued to individuals, although larger crew-served launchers are issued at higher levels of organization by military forces.

Grenade launchers are produced in the form of standalone weapons (either single-shot or repeating) or as attachments mounted to a parent firearm, usually a rifle. Larger crew-served automatic grenade launchers such as the Mk 19 are mounted on tripods or vehicles.

Some armored fighting vehicles also mount fixed arrays of short-range, single-shot grenade launchers as a means of defense.