The S-400 Triumf (Russian: C-400 ?????? – Triumf; translation: Triumph; NATO reporting name: SA-21 Growler), previously known as the S-300 PMU-3,[2] is a mobile, surface-to-air missile (SAM) system developed in the 1990s by Russia's Almaz Central Design Bureau for Marine Engineering as an upgrade to the S-300 family.

The development of the S-400 system began in the late 1980s and was announced by the Russian Air Force in January 1993.[3] On 12 February 1999 successful tests were reported at Kapustin Yar in Astrakhan, and the S-400 was scheduled for deployment by the Russian army in 2001.[4] Dr. Alexander Lemanskiy of Almaz-Antey was the Chief Engineer on the S-400 project.In 2003, it became apparent that the system was not ready for deployment. In August, two high-ranking military officials expressed concern that the S-400 was being tested with "obsolete" interceptors from the S-300P system and concluded that it was not ready for deployment.[4] The completion of the project was announced in February 2004. In April, a ballistic missile was successfully intercepted in a test of the upgraded 48N6DM missile.[5][6] In 2007, the system was approved for service.[7] Russia had accepted for service the 40N6 long-range missile for the S-400 air-defence system, a source in the domestic defense industry told TASS news agency in October 2018.[8]The S-400 Triumf and Pantsir missile system can be integrated into a two-layer defense system