K40

K40 may refer to:
 * HMS Peony (K40), a corvette of the Royal Navy
 * INS Eilat (K-40), a destroyer of the Israeli Navy
 * INS Veer (K40), a corvette of the Indian Navy
 * Piano Concerto No. 3 (Mozart), by Wolfgang Amadeus Mozart
 * Potassium-40, an isotope of potassium
 * Redmi K40, a smartphone
 * Toyota K40 transmission