A revolver is a repeating firearm that has a revolving cylinder containing multiple chambers and at least one barrel for firing. The term "revolver" refers to a handgun, but other weapons may also have a revolving chamber. These include some models of grenade launchers, shotguns, and rifles.

Though the original name was "revolving gun", the short-form "revolver" is universally used. Nearly all revolvers have six chambers in the cylinder, giving rise to the slang term "six-shooter"; however, revolvers with from four to twelve chambers have been made.

The revolver allows the user to fire multiple rounds without reloading. Each time the user cocks the hammer, the cylinder revolves to align the next chamber and round with the hammer and barrel, which gives this type of firearm its name. In a single-action revolver, the user pulls the hammer back with his free hand; the trigger pull only releases the hammer. In a double-action revolver, pulling the trigger moves the hammer back, then releases it.

The first true revolver—a flintlock—was made by Elisha Collier in 1814. The first percussion cap revolver was the Colt Paterson, invented by Samuel Colt in 1836. The first cartridge revolvers were produced around 1856 by Smith & Wesson.