Twenty Thousand Leagues Under the Seas (French: Vingt mille lieues sous les mers) is a classic science fiction adventure novel by French writer Jules Verne.

The novel was originally serialized from March 1869 through June 1870 in Pierre-Jules Hetzel's fortnightly periodical, the Magasin d'éducation et de récréation. A deluxe octavo edition, published by Hetzel in November 1871, included 111 illustrations by Alphonse de Neuville and Édouard Riou. The book was widely acclaimed on its release and remains so; it is regarded as one of the premier adventure novels and one of Verne's greatest works, along with Around the World in Eighty Days and Journey to the Center of the Earth. Its depiction of Captain Nemo's underwater ship, the Nautilus, is regarded as ahead of its time, since it accurately describes many features of today's submarines, which in the 1860s were comparatively primitive vessels.

A model of the French submarine Plongeur (launched in 1863) figured at the 1867 Exposition Universelle, where Jules Verne examined it and was inspired by it when penning his novel.

Captain Nemo walk underwater. A fragment from the book3D scene made in Twinmotion 2021.1.4.diver and submarine made in SketchUp 2021