The MG FF was a drum-fed, blowback-operated, 20 mm aircraft autocannon, developed in 1936 by Ikaria Werke Berlin of Germany.

It was a derivative of the Swiss Oerlikon FF F cannon (its FF suffix indicating Flügel Fest, for a fixed-mount, wing location from the Swiss original), with the Oerlikon FF design itself a development of the Imperial German World War I Becker 20 mm cannon, and was designed to be used in space-limited, fixed mountings such as inside aircraft wings, although it saw use as both an offensive and a defensive weapon, in both fixed and flexible format.

It saw widespread use in those roles by the German Luftwaffe, particularly during the early stages of World War II, although from 1941 onwards it was gradually replaced by the Mauser firm's 20 mm MG 151/20, which had both a higher rate of fire and muzzle velocity.

The MG FF was adapted to fire a new type of high-capacity, high-explosive "mine shell" that featured a projectile with thinner walls that allowed increased explosive charge.

With this modification it could fire the new mine shell, but accidentally using the heavier MG FF ammo could damage the gun.

Although the MG FF was often replaced with the 20 mm MG 151/20 from 1941 onwards, it saw a comeback in 1943 as the primary Schräge Musik gun in the Bf 110 (and other) night fighters, as it fit perfectly into the rear cockpit, and muzzle velocity was less important in this application (there were also stocks of surplus guns and ammunition to be used up).

When the projectile broke up, the phosphorus remained in effective parts in the target and burned for a long time.