A syntype of Homonyx cupreus Gu??rin-M??neville, 1839 (Coleoptera: Scarabaeidae: Rutelinae: Rutelini) was located, studied, and designated a lectotype. As the original description lacking adequate diagnostic characters, the species is redescribed based on the lectotype and on specimens ofHomonyx collected in Brazil that are conspecific with H. cupreus. Diagnostic characters and photographs of the type and non-type specimens are presented, and its true distribution in South America is established. Based on morphology and examination of type specimens, Homonyx chalceus bahianus Ohaus, 1913 is a new junior synonym ofHomonyx cupreus.