Ostorhinchus cookii, common names Cook's cardinalfish, Cook's soldierfish, blackbanded cardinal, blackbanded cardinalfish, is a species of marine fish in the family Apogonidae. This species grows to a maximum length of 10 cm. It is a reef fish that is also used in the aquarium industry. It is indigenous to both the northwest and western central Pacific Ocean as well as the western and eastern Indian Ocean.