K31 may refer to: * K31, a magazine-fed, straight-pull bolt-action rifle * HSwMS Visby (K31), the lead ship in the new class of Visby corvettes * K-31 (Kansas highway), a state highway in Kansas * HMS Camellia (K31) * Soviet submarine K-31, a Soviet nuclear-powered submarine that had a reactor accident * Sonata in B flat, K. 31, by Wolfgang Amadeus Mozart; see Violin Sonatas, KV 26-31 (Mozart) * Potassium-31 (K-31 or 31K), an isotope of potassium This disambiguation page lists articles associated with the same title formed as a letter-number combination. If an internal link led you here, you may wish to change the link to point directly to the intended article.