The coypu (Myocastor coypus Molina, 1782) has been reported as the definitive host of Hippocrepis fuelleborni in Argentina and Uruguay; and Hippocrepis myocastoris Babero, Cabello & Kinoed, 1979 in Chile. Specimens of M. coypus (n = 4) from the State of Rio Grande do Sul, in Brazil, were received from donations and necropsied in the laboratory. Digeneans were identified as H. fuelleborni due to the presence of ventral papillae, oblique testes and eggs with no polar filaments. The prevalence of H. fuelleborni was 25%, with a mean intensity of infection of 12 helminths/ host. The infection of M. coypus by H. fuelleborni probably occurred as a result of the ingestion of aquatic plants with metacercariae. This is the first report of H. fuelleborni parasitizing M. coypus in the State of Rio Grande do Sul, Brazil.