The Maxim gun was the first self-powered machine gun, invented by the American-born British inventor Sir Hiram Stevens Maxim in 1884. It has been called "the weapon most associated with [British] imperial conquest".

The mechanism of the Maxim gun employed one of the earliest recoil operated firing systems in history. The idea is that the energy from the recoil is used, in lieu of a locked bolt or a lever mechanism, to eject each spent cartridge and insert the next one. This made it vastly more efficient and less labour intensive than previous rapid-firing guns, such as the Gatling, Gardner, or Nordenfelt guns, which relied on actual mechanical cranking, as well as decreasing the gas buildup in the barrel, allowing the gun to fire more bullets over an extended period of time without overheating the barrel. Trials demonstrated the Maxim could fire 600 rounds per minute, equivalent to the firepower of about 30 contemporary breech-loading bolt-action rifles. Compared to modern machine guns, the Maxim was heavy, bulky, and awkward. Although a lone soldier could fire the weapon, it was usually operated by a team of men. Apart from the gunner, other crew were needed to speed reload, spot targets, and carry and ready ammunition and water. Several men were needed to move the weapon.

Maxim may refer to:

A gun is a muzzle or breech-loaded projectile-firing weapon. There are various definitions depending on the nation and branch of service. A "gun" may be distinguished from other firearms in being a crew-served weapon such as a howitzer or mortar, as opposed to a small arm like a rifle or pistol, but there are exceptions, such as the U.S. Air Force's GUU5/P. At one time, land-based artillery tubes were called cannon and sea-based naval cannon were called guns. The term "gun" evolved into a generic term for any tube-launched projectile-firing weapon used by sailors, including boarding parties and marines.

In modern parlance, a gun is a projectile weapon using a hollow, tubular barrel with a closed end — the breech — as the means of directing the projectile (as well as other purposes, for example stabilizing the projectile's trajectory, aiming, as an expansion chamber for propellant, etc.), and firing in a generally flat trajectory.

The term "gun" has also taken on a more generic meaning, by which it has come to refer to any one of a number of trigger-initiated, hand-held, and hand-directed implements, especially with an extending bore, which thereby resemble the class of weapon in either form or concept. Examples of this usage include staple gun, nail gun, glue gun, grease gun. Occasionally, this tendency is ironically reversed, such as the case of the American M3 submachine gun which carries the nickname "Grease Gun".