Le Redoutable (S 611) was the lead boat of her class of ballistic missile submarines in the French Marine nationale.
Commissioned on 1 December 1971, the boat was the first French SNLE (Sous-marin Nucléaire Lanceur d'Engins, "Device-Launching Nuclear Submarine"). The boat was initially fitted with 16 M1 MSBS (Mer-Sol Balistique Stratégique) submarine-launched ballistic missiles, delivering 450 kilotons at . In 1974, the boat was refitted with the M2 missile, and later with the M20, each delivering a one-megatonne warhead at a range over . Le Redoutable ("formidable" or "fearsome" in French) was the only ship of the class not to be refitted with the M4 missile.
Le Redoutable had a 20-year duty history, with 51 patrols of 70 days each, totalling an estimated 90,000 hours of diving and 1.27e6km of distance, the equivalent of travelling 32 times around the Earth.[1]
The boat was decommissioned in 1991. In 2000, the boat was removed from the water and placed in a purpose-built dry dock, and over two years was made into an exhibit. This was a monumental task, the biggest portion of which was removing the nuclear reactor and replacing the midsection with an empty steel tube. In 2002, the boat opened as a museum ship at the Cité de la Mer naval museum in Cherbourg-Octeville, France, being now the largest submarine open to the public and the only nearly-complete ballistic missile submarine hull open to the public — although several museums display small portions, such as sails and/or parts of rudders from such submarines. Special dinner events for organizations aboard this boat's interior spaces are offered by Cité de la Mer.