Battle of the Japan Sea (Japanese: 日本海大海戦, Hepburn: Nihonkai Daikaisen, lit. 'The Great Battle in the Japan Sea') is a 1969 Japanese epic war film directed by Seiji Maruyama, with special effects by Eiji Tsuburaya. The film stars Toshiro Mifune, Yūzō Kayama, Tatsuya Nakadai, Toshio Kurosawa, Makoto Satō, Ryutaro Tatsumi, Chishū Ryū, and Matsumoto Kōshirō VIII. In the film, the Imperial Japanese Navy and army fail in their attempts to seize Port Arthur, and the Russian Pacific Fleet bears down on the Japan Sea during the Russo-Japanese War.

The film was theatrically released in Japan by Toho on August 1, 1969 and earned ¥360 million, against a production budget of ¥350 million, during its theatrical run, making it the second-highest-grossing Japanese film of 1969.