dragonfish, any of about five species of small marine fishes comprising the family Pegasidae and the order Pegasiformes. Dragonfish are found in warm Indo-Pacific waters. They are small (to about 16 centimetres [6 1/2 inches] long), elongated fish encased in bony rings of armour. The armour is fused on the head and body but not on the tail, which is thus flexible. The pectoral fins are large, horizontal, and winglike; the pelvic fins consist of a few fingerlike rays. The mouth is small and toothless and is placed below an elongated, bony snout.
Little is known about the natural history of the dragonfish. Their relationships to other fish groups are also in doubt. One of the best known dragonfish is Pegasus volitans, a blue-eyed, brown or deep-red fish found from India to Australia.