A handgun is a firearm designed to be usable with only one hand. It is distinguished from a long gun (i.e. rifle, shotgun, submachine gun, machine gun) which needs to be held by both hands and braced against the shoulder. The two most common types of handguns are revolvers and semi-automatic pistols, although other types such as derringers and machine pistols also see infrequent usage.

Before commercial mass production, handguns were often considered a badge of office—comparable to a ceremonial sword—as they had limited utility and were more expensive than the long guns of the era. In 1836 Samuel Colt patented the Colt Paterson, the first practical mass-produced revolver, which was capable of firing five shots in rapid succession and quickly became a popular defensive weapon, giving rise to the saying, "God created men, but Colt made them equal." Today, in most of the world, handguns are primarily used by police and military officers as sidearms. However, in the United States and some other countries, handguns are also widely available to civilians and commonly carried for self-defense.