A revolver (also called a wheel gun) is a repeating handgun that has at least one barrel and uses a revolving cylinder containing multiple chambers (each holding a single cartridge) for firing. Because most revolver models hold up to six cartridges before needing to be reloaded, revolvers are also commonly called six shooters.

Before firing, cocking the revolver's hammer partially rotates the cylinder, indexing one of the cylinder chambers into alignment with the barrel, allowing the bullet to be fired through the bore. The hammer cocking in nearly all revolvers are manually driven, and can be achieved either by the user using the thumb to directly pull back the hammer (as in single-action), via internal linkage relaying the force of the trigger-pull (as in double-action), or both (as in double/single-action). By sequentially rotating through each chamber, the revolver allows the user to fire multiple times until having to reload the gun, unlike older single-shot firearms that had to be reloaded after each shot. Some rare revolver models can utilize the blowback of the preceding shot to automatically cock the hammer and index the next chamber, although these self-loading revolvers (known as automatic revolvers, despite technically being semi-automatic) never gained any widespread usage.

Although largely surpassed in convenience and ammunition capacity by semi-automatic pistols, revolvers still remain popular as back-up and off-duty handguns among American law enforcement officers and security guards and are still common in the American private sector as defensive, sporting, and hunting firearms. Famous revolvers models include the Colt 1851 Navy Revolver, the Webley, the Colt Single Action Army, the Colt Official Police, Smith & Wesson Model 10, the Smith & Wesson Model 29 of Dirty Harry fame, the Nagant M1895, and the Colt Python.

Though the majority of weapons using a revolver mechanism are handguns, other firearms may also have a revolver action. These include some models of rifles, shotguns, grenade launchers, and cannons. Revolver weapons differ from Gatling-style rotary weapons in that in a revolver only the chambers rotate, while in a rotary weapon there are multiple full firearm actions with their own barrels which rotate around a common ammunition feed.