The Grachonok class, Russian designation Project 21980 Grachonok, is a class of anti-saboteur and large guard boats being built for the Russian Navy. The class is designed to combat sabotage and terrorist forces and means in the waters off bases and near the approaches to them, as well as to assist the Border Service of the Federal Security Service of the Russian Federation in solving the problems of preservation and protection of the state border of Russia.

This is a single-deck boat with a steel hull and a wheelhouse made of aluminum-magnesium alloys, with a continuous main deck, a developed superstructure, inclined bow and transom stern. For work at the stern of the boat there is a crane. Propulsion is from a twin marine diesel engine arrangement that can propel the modern design to speeds of 23 knots in ideal conditions. Since heavy automation is built into these boats, only a crew of eight is needed for maximum function. The boat can stay at-sea for as many as five days with the onboard fuel and food stores. Aboard is the MR-231 Pal system used for navigation and the Kalmar is the main sonar fit while the MG-757 Anapa-M is the towed sonar array. An MTK-201M2 provides as eletro-optical television functionality. Armament is a DP-65A remote-controlled rocket grenade launcher and a DP-64 series grenade launcher. There is also a single 14,5-mm MTPU heavy machine gun and an Igla-1 man-portable SAM system (four missile reloads) as well as any personal weapons carried by the crew.

Anti-saboteur boat P-191 laid down 07 May 2010 at the Shipyard named after A.M. Gorky, Zelenodolsk (yard No.982), launched on July 2011, commissioned on October 2011 and was assigned to the Black Sea Fleet.

16 February 2015 the boat was renamed to P-191 Cadet.

Now in service.