A new genus, Robaloscion gen. nov., is described to include the Peruvian robalos: Sciaena wieneri Sauvage, 1883 and Sciaena starksi Evermann & Radcliffe, 1917, on the basis of all known specimens. The new genus is defined as a sciaenid with: a pair of horn-like appendages arising at the anterior extremity of the gas bladder; emarginate to lunate caudal fin; very elongate sagitta with a large, globose umbo on the outer face; small eye contained 10 to 17 times in head length. Sciaena starksi is treated as a junior synonym of S. wieneri based on examination of the type series of both species. Robaloscion wieneri is one of the largest sciaenids of the eastern Pacific, reaching a size of 1400 mm, and is distributed from northern Peru to northern Chile.