The heavy machine gun or HMG is a class of machine gun implying greater characteristics than medium machine guns.

A machine gun is a fully automatic mounted or portable firearm, designed to fire bullets in quick succession from an ammunition belt or magazine, typically at a rate of 300 to 1800 rounds per minute. Fully automatic weapons are generally categorized as submachine guns, assault rifles, battle rifles, automatic shotguns, machine guns, or autocannons.