Plongeur (French: [plɔ̃ʒœʁ]; "Diver") was a French submarine launched on 16 April 1863. She was the first submarine in the world to be propelled by mechanized (rather than human) power.
Captain Siméon Bourgeois, who made the plans, and naval constructor Charles Brun began working on the design in 1859 at Rochefort.