The Suomi-konepistooli KP-31 (Submachine Gun Finland KP-31) was a submachine gun of Finnish manufacture that was in service during World War II. It was a descendant of the M-22 prototype and the KP-26 production model, which was revealed to the public in 1925. The Suomi-konepistooli KP-31 is often abbreviated to just Suomi KP. The Suomi KP-31 went into serial production in 1931 by "Tikkakoski Oy" and most of these weapons were bought by the Finnish Defence Forces. The Finnish Defence Forces were equipped with about four thousand Suomi KP-31 submachine guns when the Winter War started.