The Peabody action was an early form of breechloading firearm action, where the heavy breechblock tilted downwards across a bolt mounted in the rear of the breechblock, operated by a lever under the rifle. The Peabody action most often used an external hammer to fire the cartridge.

In firearms terminology, an action is the functional mechanism of a breech-loading firearm that handles the ammunition cartridges, or the method by which that mechanism works. Actions are technically not present on muzzleloaders, as all those are single-shot firearms with a closed off breech with the powder and projectile manually loaded from the muzzle. Instead, the muzzleloader ignition mechanism is referred to as the lock.