Barrack buster is the colloquial name given to several improvised mortars, developed in the 1990s by the engineering unit of the Provisional Irish Republican Army (IRA).

A mortar is today usually a simple, lightweight, man-portable, muzzle-loaded cannon, consisting of a smooth-bore metal tube fixed to a base plate with a lightweight bipod mount and a sight. Mortars are typically used as indirect fire weapons for close fire support with a variety of ammunition. Historically mortars were heavy siege artillery. Mortars launch explosive shells in high-arching ballistic trajectories.