The Buyan class, (Russian: ????, lit. 'Buyan'), Russian designations Project 21630 Buyan and Project 21631 Buyan-M, are series of corvettes (small artillery and missile ships in Russian classification) developed by Zelenodolsk Design Bureau for the Russian Navy. Since 2010, all subsequent vessels are being constructed as improved Project 21631 subclass, incorporating greater tonnage, stealth technology and the 3S-14 vertical launching system for either Kalibr or Oniks anti-ship cruise missiles, significantly enhancing combat capabilities. The ships are primarily designed for operations within littoral zones to protect Russia's vast coastal areas. Due to the small tonnage, they can operate even within shallow parts of oceans and seas and Russia's river system. The export variant is known as Project 21632 Tornado.