A general purpose machine gun or GPMG in concept is a compromise weapon, a machine gun intended to be capable of doing the tasks of a light machine gun, medium machine gun while at the same time being man-portable, but performance in either role may be inferior to a weapon specifically for that that role. In practice, they are medium air-cooled machine guns firing full power rifle cartridges such as 7.62 NATO. They are generally operated from a stationary (prone) position from either a bipod or tripod, being too powerful or heavy to be fired usefully on the move.

The modern GPMG is a medium machine gun which operates as a support weapon. In the modern times it has become a name simply for a medium machine gun that is used in a variety of roles, but intially the concept as it was introduced with MG-34 in 1935 was for a weapon that could replace both light and heavy machine guns (as machine guns had already been used in many roles). The idea that a weapon could replace lighter support weapons and heavier one's enjoyed some success in the couple of decades after WWII but has gradully fallen out of favor.

Some nations use the GMPG name (or a translation of it) for their weapon but didn't actually apply the concept, and some did the reverse. Overall the GPMG's concept itself has not been especially successfull, with lighter machine guns continuing to be used as well as heavier designs. They were successfull in supplanting heavy water-cooled designs firing the same caliber, but this mostly due to that type of weapon not being required by modern warfare anymore. In the US for example, the M240 could be considered a GPMG, but it does not fufull the GPMG concept. The ligher M249 is the main light squad support weapon and on the heavier side Mini-guns and the M2 machine gun are used.

In the British Army the current GPMG is the L7 and in the US Army the M240 which are both versions of the FN MAG, FN Mitrailleuse d'Appui General (general purpose machine gun).