The 2A42 is a late Cold War era 30mm autocannon of Soviet origin. It was developed somewhere in the 1970's and was selected to arm the new BMP-2. The 2A42 autocannon significantly improved the lethality and combat range of the BMP-2 compared to the BMP-1 with its 73mm low pressure cannon. The 2A42 has also been used on a variety of other platforms and its 30x165mm ammunition is used by various other Soviet autocannon.

The 2A42 is a gas double belt feed gas operated electrically powered weapon that requires external power. The long barrel is rifled and has a double baffle muzzle brake. The rate of fire is selectable to low and high. Due to its significant recoil the strength requirements on the mount are high.

The 2A42 fires the now common 30x165mm round that was specifically developed for this weapon. Several types of ammunition are available. The low rate of fire setting is 200 to 300 rpm and the high setting about 550 to 800 rpm. The effective range is 1.5 km versus armored vehicles. The effective range for the high explosive rounds is about 2 km versus infantry, vehicles and aircraft although it has a slant range of 4 km.

The main use of the 2A42 is as main armament of the BMP-2 mechanized infantry combat vehicle. Other vehicles that use the 2A42 are the BMD-2, BMD-3 and BTR-90. The 2A42 is also used on the Mi-28 Havoc and Ka-50 Hokum helicopters, making it one of the most powerful helicopter guns in use.