A rotary cannon, rotary autocannon, rotary gun or Gatling cannon, is any large-caliber multiple-barreled automatic firearm that uses a Gatling-type rotating barrel assembly to deliver a sustained saturational direct fire at much greater rates of fire than single-barreled autocannons of the same caliber. The loading, firing and ejection functions are performed simultaneously in different barrels as the whole assembly rotates, and the rotation also permits the barrels some time to cool. Rotary cannons, external or self-driven are used in aircraft over reciprocating bolt autocannons which are more prone to jamming in high g environments. The rotating barrels on nearly all modern Gatling-type guns are powered by an external force such as an electric motor, although internally powered gas-operated versions have also been developed.

A multiple-barrel firearm is any type of firearm with more than one gun barrel, usually to increase the rate of fire or hit probability and to reduce barrel erosion or overheating.