Banryū was a ship of the Tokugawa Navy, and following the collapse of the shogunate, was operated by Tokugawa loyalists under the Republic of Ezo during the Boshin War in Japan. An armed iron hulled screw-propelled schooner, she had a length of 41.8 metres, a breadth of 5.45 metres, a draught of 3.23 metres, and weighed 370 tons. She was armed with four 12-pounder bronze cannons.

The Republic of Ezo was a short-lived separatist state established in 1869 on the island of Ezo, now Hokkaido, by a part of the former military of the Tokugawa shogunate at the end of the Bakumatsu period in Japan. It was the first government to attempt to institute democracy in Japan, though voting was allowed only to the samurai caste. The Republic of Ezo existed for five months before being annexed by the newly established Empire of Japan.