A machine pistol is a self-loading pistol capable of burst or fully automatic fire. It can also be used to describe a stockless handgun-style submachine gun. The term is a calque of Maschinenpistole, the German word for submachine guns. Machine pistols were developed during World War I and originally issued to German artillery crews who needed a self-defense weapon that is lighter than a rifle but more powerful than a standard semi-automatic pistol. This concept would eventually lead to the development of the personal defense weapon or PDW. Today, machine pistols are considered special purpose weapons with limited utility, with their original niche being filled with either the PDW, carbines, or simply more modern semi-automatic sidearms. Contributing to their already-fringe use, without a shoulder stock and training, machine pistols can be difficult to control for all but the best shooters.

The Austrians introduced the world's first machine pistol, the Steyr Repetierpistole M1912/P16, during World War I. The Germans also experimented with machine pistols, by converting various types of semi-automatic pistols to full-auto, leading to the development of the first practical submachine guns. During World War II, machine pistol development was widely disregarded in favor of submachine gun mass-production. After the war, machine pistols development was limited and only a handful of manufacturers would develop new designs, with varying degrees of success.