Three new species of the weevil genus Achia Champion are described: A. urvilleae Clark and Burke from the state of Santa Catarina, Brazil and Misiones Province, Argentina; A. uniformis Clark and Burke from Bolivia; and A. boliviana Clark and Burke from Bolivia and Salta and Santiago del Estero provinces, Argentina. Keys and illustrations to facilitate identification of the species are provided. New host plant records for these and other species of Achia include: Urvillea ulmacea Kunth for A. urvilleae; Urvillea chacoensis Hunz. for A. boliviana; Serjania laruotteana Cambess for A. ancile Burke; and Serjania fuscifolia Radlk. for A. affinis Hustache. The genus Achia is apparently most closely related to Cissoanthonomus Hustache and Cionopsis Champion. These three genera have the head constricted behind the eyes, profemora greatly enlarged, and their known hosts are plants of the family Sapindaceae.