How big is the world's biggest submarine?

Answer 1

The biggest submarine ever built is still the Russian Navy's Typhoon-class (NATO reporting name) Ballistic Missile Submarine, with a reported length of 175 m (574 ft 2 in), and a beam of 23 m (75 ft 6 in).

The Typhoon class submarines were built to compete with the U.S. Ohio-class FBM Submarines, which are 560 ft (170 m) long and 42 ft (13 m) wide. One Typhoon (TK-208 Dmitriy Donskoy) is still in commission and active in the Russian Navy, while 2 others remain in the Russian Naval Reserve.