Acanthurus bahianus was first formally described in 1855 by the French naturalist François-Louis Laporte, comte de Castelnau with its type locality give as Bahia in Brazil.

[6] Acanthurus bahianus are known by their oval bodies with uniform color (usually blue-gray to dark brown), the pale to dark marking around the eyes, and the light yellow is now found on their bodies.

Ocean surgeons have a total of 9 spines on their dorsal fins and between 23 and 26 soft rays.

Their caudal fins are roughly emarginate, and the surgeonfish's body and head are both deep and compressed.

[9] In the southern and central Atlantic, the Ocean surgeon can be found along the coast of Brazil from the states of Maranhão, south to Stanta Caterinha.