The Bofors 40 mm Automatic Gun L/70,, is a multi-purpose autocannon developed by the Swedish arms manufacturer AB Bofors during the second half of the 1940s as a modern replacement for their extremely successful World War II-era Bofors 40 mm L/60 gun-design. It was initially intended as a dedicated anti-aircraft weapon, being sold as Bofors 40 mm Automatic A.A. Gun L/70, but has since its conception been redeveloped into a dedicated multi-purpose weapon capable of firing both sabot projectiles and programmable ammunition. The Bofors 40 mm L/70 design never achieved the same popularity and historical status as the original L/60 design but has still seen great export and popularity to this day, having been adopted by around 40 different nations and even being accepted as NATO-standard in November 1953. It is still being produced and sold, and several variants exist for both field and naval applications. A notable variant is the Bofors 40/70B "light armored vehicle variant" which is in use on the Swedish Strf 9040 and Korean K21 infantry fighting vehicles.

An autocannon, automatic cannon or machine cannon is a fully automatic gun that is capable of rapid-firing large-caliber armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bullets) fired by a machine gun. Autocannons have a longer effective range and greater terminal performance than machine guns, due to the use of larger/heavier munitions, but are usually smaller than tank guns, howitzers, field guns, or other artillery. When used on its own, the word "autocannon" typically indicates a non-rotary weapon with a single barrel. When multiple rotating barrels are involved, such a weapon is referred to as a "rotary autocannon" or occasionally "rotary cannon", for short.