A pump-action rifle or shotgun is one in which the handgrip can be pumped back and forth in order to eject a spent round of ammunition and to chamber a fresh one. It is much faster than a bolt-action and somewhat faster than a lever-action, as it does not require the trigger hand to be removed from the trigger whilst reloading. When used in rifles, this action is also commonly called a slide action.

The term pump-action can also be applied to various airsoft guns and air guns, which use a similar mechanism to both load a pellet and compress a spring piston for power, or pneumatic guns where a pump is used to compress the air used for power. See the airgun article for information on how spring piston and pneumatic airguns work.

The cycling time of a pump-action is quite short, often less than that of some semi-automatic designs. The manual operation gives a pump-action the ability to cycle rounds of widely varying power that a gas or recoil operated firearm would fail to cycle, such as most less-than-lethal rounds. The simplicity of the pump-action relative to a semi-automatic design also leads to improved durability and lower cost. It has also been noticed that the time taken to work the action allows the operator to identify and aim on a new target, avoiding a "spray and pray" usage.