A revolver is a repeating handgun with at least one barrel and a revolving cylinder containing multiple chambers (each holding a single cartridge) for firing. Because most revolver models hold six cartridges before needing to be reloaded, revolvers are commonly called six shooters or sixguns. Due to their rotating cylinder mechanism, they may also be called wheel guns.

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. 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.

The hammer cocking in nearly all revolvers is manually driven and can be cocked either by the user using the thumb to directly pull back the hammer (as in single-action), or via internal linkage relaying the force of the trigger-pull (as in double-action), or both (as in double-action/single-action).

Some rare revolver models 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.

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 autocannons. 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.

Famous revolver 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.

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.

In the development of firearms, an important limiting factor was the time required to reload the weapon after it was fired. While the user was reloading, the weapon was useless, allowing an adversary to attack the user. Several approaches to the problem of increasing the rate of fire were developed, the earliest involving multi-barrelled weapons which allowed two or more shots without reloading. Later weapons featured multiple barrels revolving along a single axis.