TOS-1 (Russian: ТОС-1 – тяжёлая огнемётная система, English: Heavy Flamethrower System) is a Soviet 220mm 30-barrel (original system, Ob.634 or TOS-1M) or 24-barrel (Ob.634B or TOS-1A) multiple rocket launcher and thermobaric weapon mounted on a T-72 tank chassis. TOS-1 was designed for defeating enemy personnel in fortifications, in open country, and in lightly armoured vehicles and transport. First combat tests took place in 1988–1989 in the Panjshir Valley during the Soviet war in Afghanistan. The TOS-1 was shown for the first time in public in 1999 in Omsk.
The TOS-1 is not used by the artillery units of the Russian Armed Forces but is found in NBC defense units (Russian: войскa радиационной, химической и биологической защиты (РХБЗ)).
The idea of a heavy short-range MLRS to launch rockets equipped with incendiary and thermobaric warheads arose in the late 1970s. The combat system consisting of the combat vehicle, rockets, and loading vehicle was developed in early 1980s at KBTM in Omsk and was named TOS-1, remaining a secret development for a long time.