Nautilus is the name of several submarines, submersibles, and semisubs. They are named for the nautilus.

• Nautilus (1800 submarine), a French First Republic sub designed by Fulton, considered the first practical sub (1800–1802)
• French submarine Nautilus (1930), a French Navy sub, a Saphir-class submarine (1927–1947)
• HMS Nautilus (1914), a UK Royal Navy sub, the largest RN sub at service entry (1914–1922)
• USS Nautilus (SS-168), a U.S. Navy sub, a Narwhal-class submarine (1930–1945)
• USS Nautilus (SSN-571), a prototype U.S. Navy sub, the first nuclear submarine (1954–1980)

• Nautilus (O-class submarine), a former U.S. Navy submarine, a O-class submarine (1917–1931)
• UC3 Nautilus, a Danish civilian home-built sub, part of a 2017 murder case (2009–2018)

• Nautilus (fictional submarine), a fictional submarine created by Jules Verne. Found in the novels Twenty Thousand Leagues Under the Seas (1870) and The Mysterious Island (1874)

• Nautilus (disambiguation)

This article includes a list of ships with the same or similar names. If an internal link for a specific ship led you here, you may wish to change the link to point directly to the intended ship article, if one exists.