A new species of peacock bass, Cichla cataractae, is distinguished from all congeners by molecular evidence and unique patterns of adult and juvenile pigmentation. Juveniles (<150 mm SL) have sides of body dominated by a series of three conspicuous dark blotches with the one below soft dorsal fin largest, attenuated posteriorly (long teardrop shape) but distinctly separated from elliptical caudal blotch; same blotches eventually with pale border (ocellated) in largest juveniles. Adult pattern on sides dominated by two distinct dark blotches, each one ocellated; anterior blotch rounded, located below anterior base of spinous dorsal fin and not extending above anterior lateral line; posterior blotch highly irregular in shape, located below soft dorsal fin and often displaced dorsally; additional dark blotch below posterior base of spinous dorsal fin generally absent or small, ocellated or not, and level with anterior blotch; vertical bars on sides generally absent or faint; postorbital stripe always present, highly broken into irregular series of dark spots, each one usually ocellated. Cichla cataractae is endemic to the Essequibo Basin where it typically inhabits rocky shoals in river channels with swift current. The new species is sympatric with the more widely distributed C. ocellaris, a species that prefers lentic habitats. Molecular analysis supports C. cataractae as a distinct lineage in a clade of Cichla containing C. temensis, C. melaniae, C. mirianae, C. piquiti and C. pinima. The oldest extant specimens of the new species were collected by Carl H. Eigenmann in 1908 and documented in his seminal "The Freshwater Fishes of British Guiana" (Eigenmann, 1912).