Plectranthias nazcae, a new species of anthiine serranid fish, is described from five specimens collected on the Nazca Ridge in the eastern South Pacific, some 1500 kilometers west of Chile, at about 26°S. The new species is distinguished from all other species of Plectranthias by the following combination of characters: total gillrakers on first gill arch 28–31, circum-caudal-peduncular scales 17 or 18, tubed lateral-line scales 36–42, certain body proportions, and apparently coloration. Comments on the coloration of P. exsul and a key to the three known eastern Pacific species of Plectranthias are provided.