Paracanthurus hepatus is a species of Indo-Pacific surgeonfish. A popular fish in marine aquaria, 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 Iyana Acanthurus coeruleus), royal blue tang, hippo tang, flagtail surgeonfish, Pacific regal blue tang and blue surgeonfish.