The leaf chafer tribe Alvarengiini Frey, a long-neglected taxon that has been overlooked in the biodiversity literature from its inception, is revised for the first time. As a result of this research, the tribe is composed of two species in two genera distributed from Bahia, Brazil (in the north), to Paraná, Brazil (in the south), and Paraguay. Two synonyms are proposed: Alvarengius silphoides Frey, syn. nov. for Ottokelleria dispar (Burmeister) and Alvarengius Frey, syn. nov. for Ottokelleria D'Andretta & Martínez. A new genus is described, Carinochilus, gen. nov., and includes one species: Carinochilus marginatus (Burmeister), comb. nov. The lectotype for O.dispar and a neotype for C.marginatus are designated. We provide an identification key to the tribes of Rutelinae (in English and Portuguese) and incorporate classification changes in the subfamily. A key for the identification of Alvarengiini genera and species is also provided. All taxa are circumscribed and illustrated, and distributional data are synthesised in maps. © 2024 Australian Entomological Society.