The BM-21 Grad ('Hail') was one of the most widely produced Soviet multiple rocket launcher vehicles of the Cold War, inheriting the light, low-cost design philosophy that characterized previous Soviet MRLs like the wartime Katyusha. The BM-21 is based on the chassis of the Ural-375D 6 x 6 truck chassis, with the firing equipment located in the cabin and a 40-round 122-mm launcher on the rear of the vehicle. The launcher features four rows of 10 tubes each and can be readied for fire in three minute; a full 40-round salvo can be fired in 20 seconds although individual or selective ripple fire can also be applied. Reloading is done by the crew manually with the support of a 9F37 resuppply vehicle. The BM-21 is assigned at a divisional level in a batallion of 12 launchers or 18 in wartime, for a total of 720 rockets in a single salvo with a maximum range of 20.4 km using conventional ammunition or up to 40 km with special projectiles. In Soviet service, it was first used in combat during the 1969 Sino-Soviet border conflict, and later in the Soviet-Afghan War and Chechen wars. Thanks to its affordability, the BM-21 has been one of the most widely exported vehicles of the Cold War, with virtually every Soviet client state adopting it, with local modifications and license production also undertaken. It is particularly widespread in Africa and the Middle East where it has been involved in dozens of regional conflicts, making it one of the most widely used combat vehicles of the post-war period.

Development of the BM-21 Grad began in the 1950s and it entered service in the USSR in 1963. It is also known by its NATO designation of BM-21a or M1964. Numerous variants have been built beginning with the BM-21V or BM-21 Grad-V (Vozdushnodesantii) which is a lighter, airborne variant fitted on a GAZ-66B 4 x 4 chassis and a 12-round launcher. Another lighter version compared to the original is the BM-21M based on a ZIL-131 6 x 6 chassis and a 36-round launcher. A similar launcher has been fitted on the MT-LB tracked chassis where it is known as the BM-21 Grad-1. A variant designed for protection of naval bases is known as the BM-21PD Damba, while another naval version with a 22-round launcher is known as the A-215 Grad-M. Numerous foreign variants also exists, often with the BM-21 launcher system mounted on a local chassis.