Soviet S-class submarine
 The S-class or Srednyaya (Russian: Средняя medium) submarines were part of the Soviet Navy's underwater fleet during World War II. Unofficially nicknamed Stalinets (Russian: Cталинец follower of Stalin; not to be confused with the submarine L-class L-2 Stalinets of 1931) boats of this class were the most successful and achieved the most significant victories among all Soviet submarines.