Poseidon is the god of the sea in ancient Greek mythology. Poseidon may also refer to: Posidonius, ancient Greek astronomer and geographer. Poseidon (fictional ship), featured in both of Paul Gallico's novels and the four film adaptations. Poseidon (Saint Seiya), manga villain. The Poseidon Adventure (1972 film), a 1972 film based on Paul Gallico's novel. Beyond the Poseidon Adventure, a 1979 sequel to the first film, based on a second book by Paul Gallico that had been commissioned by the film makers.