Maritrema orensensis sp. n. (Digenea: Microphallidae) from Balneario Orcnsc, Buenos Aires province, Argentina, is described. Adults of M. orensensis were collected from the intestine of the kelp gull Larus dominicanus Lichtenstein, 1823 (Aves: Laridae) and differ from adults of other related species, principally, in the shorter intestinal caeca and the incomplete ring of vitelline follicles.