The Russian Mk 941-U SSBN (Strategic Submarine Ballistic Nuclear) 'Typhoon', of the 'Shark' (Akula) - class, is the largest submarine in the world. The Typhoon was included in the Guinness Record Book at the beginning of the 1980s. Its total displacement makes up about 50,000 tons; it carries 24 ballistic missiles capable of being launched underwater. Six submarines of this kind were constructed in Severodvinsk. The unique sub was a response to the US's construction of the 'Ohio' nuclear submarine with 24 ballistic missiles on board. However, the Typhoon, constructed at Russia's famous design bureau Rubin under the guidance of famous designer Spassky, surpassed the Ohio: The Typhoon is still the largest submarine in the world. One of them, named 'Dmitry Donskoi', underwent a costly and lengthy refurbishment and was launched on the 26th of June 2002 at Sevmash ship-yard. Mk 941-U Akula SSBN Main specifications Length .......................... 172 meters Beam ............................ 22.8 meters Underwater displacement .................... 50,000 tons Underwater speed ................ Over 30 knots Weaponry: 24 ICBM-s replete with 10 nuclear warheads each Two torpedo tubes (one 533-mm torpedo tube and one 650-mm torpedo tube) 36 torpedoes ICBM range ...................... Up to 10,000 km Maximum diving depth .................... 500 meters Operational diving depth .................... 380 meters Endurance ....................... 120 days Crew ............................ 163 men

Hmmmmm...a little correction to a previously posted answer: The Soviet Typhoon class ballistic missile submarine is indeed the largest, by far, of any submarine ever built. She was designed to lurk about under the Polar ice cap for up to six months (180 days) or more at at time. She was (and yes, I know the Soviet naval tradition uses the masculine pronoun...bear with me and my own traditions!): 24,500 tons max displacement on the surface 48,000 tons max displacement submerged. 574 feet long 75 feet wide 20 missile tubes Compare this to the US Ohio class: 16,764 tons surface displacement 18,759 tons submerged displacement 560 feet long 42 feet wide 24 missile tubes And YES, the Typhoon DOES have a swimming pool for the use of it's crew...though it's really more of an oversized hot tub by comparrison. It's only about 8-10 feet long. But still...it's a pool on a submarine! http://en.wikipedia.org/wiki/Typhoon_class_submarine http://en.wikipedia.org/wiki/Ohio_class_submarine The Typhoon is truely one MONSTER of a submarine.