K39

K39 may refer to:
 * 15 cm Kanone 39, a German heavy gun used in the Second World War
 * Junkers K 39, a German prototype reconnaissance-bomber built 1926
 * K-39 (Kansas highway), a state highway in Kansas
 * Piano Concerto No. 2 (Mozart), K. 39, by Wolfgang Amadeus Mozart
 * Potassium-39 (K-39 or 39K), an isotope of potassium