The Hotchkiss gun can refer to different products of the Hotchkiss arms company starting in the late 19th century. It usually refers to the 1.65-inch (42 mm) light mountain gun; there were also a navy (47 mm) and a 3-inch (76 mm) Hotchkiss guns. The 42 mm gun was intended to be mounted on a light carriage or packed on two mules to accompany a troop of cavalry or an army travelling in rough country.

The QF 3-pounder Hotchkiss or in French use Canon Hotchkiss à tir rapide de 47 mm were a family of long-lived light 47 mm naval guns introduced in 1886 to defend against new, small and fast vessels such as torpedo boats and later submarines. There were many variants produced, often under license which ranged in length from 32 to 50 calibers but 40 caliber was the most common version. They were widely used by the navies of a number of nations and often used by both sides in a conflict. They were also used ashore as coastal defense guns and later as an anti-aircraft gun, whether on improvised or specialized HA/LA mounts.