Trinigyrus mourei sp. n. (Dactylogyridae) is described from an Amazonian armoured catfish, Hypostomus emarginatus (Loricariidae) in Brazil. The new species closely resembles T. hypostomatis HANEK, MOLNAR & FERNANDO, 1974, from which it differs mainly by having: 1) a more robust copulatory organ; 2) a non-articulated accessory piece; and 3) comparatively longer haptoral appendages