Atragon (海底軍艦 Kaitei Gunkan, lit. Undersea Warship) is a 1963 tokusatsu science-fiction and fantasy film produced by Toho, loosely based on the 1900 Japanese adventure novel The Undersea Warship: A Fantastic Tale of Island Adventure written by Shunro Oshikawa. The film was released to Japanese theaters on December 22, 1963 and to American theaters in December 1964.