Blakiston's fish owl, the largest living species of owl, is a fish owl, a sub-group of eagle-owls that specialize in hunting in riparian areas. It is native to China, Japan, and the Russian Far East. This species is a part of the family known as typical owls (Strigidae), which contains most species of owl. Blakiston's fish owl and three other piscivorous owls are placed with some eagle-owls in the genus Ketupa. Its habitat is riparian forest with large, old trees for nest sites near lakes, rivers, springs, and shoals that do not freeze in winter. Henry Seebohm named this bird after the English naturalist Thomas Blakiston, who collected the original specimen in Hakodate on Hokkaidō, Japan in 1883.

Ketupa is a genus of owls in the family Strigidae. The genus formerly contained just three species, the fish owls but based on the results from a genetic study published in 2020, the generic boundaries were altered. The genus now contains twelve species, nine of which were formerly placed in the genus Bubo.