P81

P81 may refer to:


 * Consolidated Vultee XP-81, an American experimental fighter aircraft
 * HMAS Acute (P 81), a patrol boat of the Royal Australian Navy
 * HMS Varne (P81), a submarine of the Royal Navy
 * INS Katchall (P81), a corvette of the Indian Navy
 * Papyrus 81, an early copy of the New Testament in Greek
 * P81, a state regional road in Latvia