Kaiyō Maru (開陽丸) was one of Japan's first modern warships, a frigate powered by both sails and steam.

Kaiyō Maru was ordered in 1863, and built by Cornelis Gips and Sons, at Dordrecht, Netherlands, for a sum of 831,200 guilders.

[8] Kaiyō Maru became the flagship of the navy of the Ezo Republic, but she soon was wrecked off Esashi, Hokkaido, Japan, during a storm on 15 November 1868.

[9] The guns and ship chandlery of Kaiyō Maru were discovered on the seafloor on 14 August 1968 by the submarine Yomiuri-Gō (読売号).

She is now on display at the docks in Esashi and has become a tourist attraction showing the salvaged remains of the original ship.