The Soviet Union/Russian Navy Project 705 (Лира/Lira, “Lyre”) was a submarine class of hunter/killer nuclear powered vessels (abbreviated PLA: Podvodnaya lodka atomnaya, nuclear submarine). The class is also known by the NATO reporting name of Alfa. They were the fastest and deepest diving class of military submarines built,with only the prototype K-278 Komsomolets (NATO “Mike” class) exceeding in crush depth and the prototype K-222 (NATO “Papa” class) exceeding in submerged speed.