Alcichthys elongatus is a fish in the family Cottidae (sculpins), and the only valid member of its genus. It was described by Franz Steindachner in 1881. It is a marine, boreal fish which is known from the northwestern Pacific Ocean, including the Sea of Okhotsk and Japan. It dwells at a depth range of 15 to 269 m (49 to 883 ft), and inhabits rocky reefs. Males can reach a maximum total length of 44 cm (17 in), but more commonly reach a TL of 31.5 cm (12.4 in). The maximum recorded weight is 1 kg (2.2 lb).