The Secret of the Island is a novel by Jules Verne, published in 1874. The original edition, published by Hetzel, contains a number of illustrations by Jules Férat. The novel is a crossover sequel to Verne's famous Twenty Thousand Leagues Under the Sea and In Search of the Castaways, though its themes are vastly different from those books.

During the American Civil War, five Northern prisoners of war escape during the siege of Richmond, Virginia by hijacking a hot air balloon. The escapees are Cyrus Smith, a railroad engineer in the Union army (named Cyrus Harding in Kingston's version); his ex-slave and loyal follower Neb (short for Nebuchadnezzar); Bonadventure Pencroff, a sailor (who is addressed only by his surname; in Kingston's translation, he is named Pencroft); his protégé and adopted son Harbert Brown (called Herbert in some translations); and the journalist Gedéon Spilett (Gideon Spilett in English versions). The company is completed by Cyrus' dog "Top".