An ammunition storage and feeding device within or attached to a repeating firearm is called a magazine. Magazines may be vital to the firearm fixed or removable. The magazine works by moving the cartridges stored in the magazine into a position where they may be loaded into the chamber by the action of the firearm. The detachable magazine is often referred to as a clip. The usage is not encouraged by many authorities on firearms but is nonetheless commonplace.

Magazines come in a variety of shapes and sizes. The earliest magazines appeared not on firearms, but rather on air guns. There are those that use bolt action express rifles that hold only a few rounds and those like machine guns that hold hundreds of rounds. Since the magazine is a necessary part of most repeating firearms, they are often the focus to regulation by gun control laws seeking to limit the number of cartridges they hold. A magazine gun is a gun that uses a magazine to load ammunition.