Prionacalus White, 1845, a genus restricted to western South America from Colombia to northern Argentina, is revised. Of the 15 species currently described, seven are considered as distinct and redescribed herein. The following five new synonymies are proposed: Prionacalus gunteri Gahan, 1894 is removed from synonymy with Prionacalus buckleyi Waterhouse, 1872 and proposed as a new synonym of Prionacalus cacicus (White, 1845); Prionacalus simonsi Waterhouse, 1900 is a new synonym of éPrionacalus atys White, 1850; Prionacalus giovannii Hüdepohl, 1985 is a new synonym of Prionacalus whymperi Bates, 1892; Prionacalus trigonodes Bates, 1892, currently a synonym of P buckleyi, is proposed as a new synonym of P. whymperi; and P. buckleyi is a new synonym of Prionacalus iphis White, 1850. The following earlier synonymies are accepted: Prionacalus emmae Kolbe, 1902 and Prionacalus whitei Waterhouse, 1900 are synonyms of P. buckleyi (and consequently, synonyms of P. iphis); syntype female of Psalidognathus wallisi Taschenberg, 1870 is a synonym of P. cacicus. Waterhouse (1872) is considered the author of the designation of the lectotype for Prionacalus iphis. The designation of a lectotype for P whymperi by Quentin and Villiers is considered invalid. Lectotypes are designated for P. whymperi, P. buckleyi, and Prionacalus uniformis Waterhouse, 1900. A key to species is provided and all species are figured.