A handgun is a firearm designed to be handheld, in either one or both hands. This characteristic differentiates handguns as a general class of firearms from long guns such as rifles and shotguns (which usually can be mounted against the shoulder).

Major handgun subtypes are the revolver and pistol; other subtypes include derringers, single-shot pistols, semi-automatic pistols, pepperboxes, and machine pistols.

The overlapping variations in meaning of the words "pistol" and "handgun" are discussed below.

Although handgun use often includes bracing with a second hand, the essential distinguishing characteristic of a handgun is its facility for one-handed operation.