An 1895 model Gatling Gun.

The Gatling gun is a gunpowder field weapon invented in the 1860s which used multiple rotating barrels turned by a hand crank. Unlike earlier weapons, such as the mitrailleuse, which had limited capacity and long reloading times, the Gatling gun was reliable, easy to load, and had a high firing rate. The gun was designed by the American inventor Richard J. Gatling, in 1861 and patented in 1862.

The Gatling gun may have been the first "Machine Gun", depending on how 'machine gun' is defined, as it was capable of firing continuous bursts of fire. Unlike designs like the Maxim gun, which operate the mechanism using a fraction of the power of the fired cartridge, the Gatling gun relies on external power, such as a hand crank, or motor. Some later Gatling-type weapons diverted gas from the barrels to spin the rotating barrels.

The term Gatling gun is still used, to refer to rotating-barrel cannons such as M61 Vulcan 20mm cannon and its younger brother the GAU-12 Equalizer used in the AC-130 gunship.