The mitrailleuse was a mid-19th century precursor to the machine gun. Invented in France in the late 1860s, it was technically a volley gun - that is, rather than firing in sequence, it could discharge all of its rounds at once.

The weapon consisted of many rifled barrels (anything up to 37 in number) arranged in a cylinder and mounted on a conventional artillery chassis. The barrels were open at the breech and would be loaded simultaneously, with the cartridges mounted in a disk which was clamped against the barrels. All of the cartridges would then be exploded either simultaneously or in rapid sequence by turning a crank, producing a (theoretically) devastating hail of fire.

In practice, however, the mitrailleuse was singularly ineffective. Much had been promised of it before the Franco-Prussian War of 1870 - it was said to be capable of firing 125 rounds per minute while accurate at two thousand yards - but its flaws quickly became apparent when it entered the battlefield. The gun and its carriage were heavy and cumbersome and its reloading time was long. Mitrailleuses were deployed in batteries but failed to make much impact on the Prussians, due to a combination of their inherent flaws and poor tactical handling. The weapon was rapidly overtaken by new and better guns such as the Maxim machine gun.

While the mitrailleuse was technically not a machine gun, the firing being manually driven rather than fully automatic, the word mitrailleuse is still used in French as a synonym for "machine gun". The word is derived from mitraille, "small shot", from the Old French mistraille, "pieces of money".

Preserved mitrailleuses can still be seen in a number of museums, notably at Les Invalides in Paris.