Heniochus monoceros, the masked bannerfish, is a marine ray-finned fish, a butterflyfish belonging to the family Chaetodontidae.

The first band masks its face starting at its mouth, and runs to the base of the first rays of the dorsal fin including at the same time its snout and eyes.

the masked bannerfish has a small growth on the axis of the forehead from which radiates a bright whitish to yellowish area.

Within this yellow area close to the caudal peduncle, a brown-yellow blotch, variable in size from one fish to another, emerges.

The masked bannerfish is widespread throughout the tropical and subtropical waters of the Indo-Pacific area from the eastern coast of Africa to Polynesia and from south Japan to New-Caledonia).