Paracanthurus hepatus is a species of Indo-Pacific surgeon fish. It is the only member of the genus Paracanthurus. A number of common names are attributed to the species, including regal tang, palette surgeonfish, blue tang (leading to confusion with the Atlantic species Acanthurus coeruleus), royal blue tang, hippo tang, flagtail surgeonfish, Pacific regal blue tang, and blue surgeonfish.
Paracanthurus hepatus has a royal blue body, yellow tail, and black “palette” design. The lower body is yellow in the west-central Indian Ocean. It grows to 30 cm. Adults typically weigh around 600gr and males are generally larger than females. This fish is rather flat, like a pancake, with a circular body shape, a pointed snout-like nose, and small scales.