Purpose <p>A new species of <i>Gussevia</i> Kohn et Paperna, 1964 (Monopisthocotyla, Dactylogyridae) is described based on specimens recovered from the gills of <i>Astronotus ocellatus</i> (Agassiz, 1831) (Cichliformes, Cichlidae) collected in the Ubaldinho weir, state of Ceará, Brazil.</p> Materials and methods <p>Some obtained monopisthocotylans were mounted on slides using Gray and Wess medium and studied using an optical microscope with a phase-contrast. Illustrations were made using a drawing tube attached to a Leica DM750 microscope and vectorized using Inkscape 1.4 software.</p> Results <p><i>Gussevia lamarckii</i> n. sp. is characterized by having an accessory piece nonarticulated with the MCO base, comprising two dorsal subunits, one Y-shaped and the other one rod-shaped; and an elongated peduncle. Furthermore, the new species can be easily distinguished from the other congeners by possessing (1) a ventral anchor with an external protuberance at the junction between the root and the shaft, and (2) a superficial groove at the base of the dorsal anchor.</p> Conclusions <p>This study presents a new species of the genus <i>Gussevia</i>, the fourth described from <i>Astronotus</i> fish and the first from <i>A. ocellatus</i> and the aquatic ecosystems of the Caatinga domain.</p>