Mesocoelium lanfrediae sp. nov. (Digenea: Mesocoeliidae) inhabits the small intestine of Rhinella marina (Am-phibia: Bufonidae) and is described here, with illustrations provided by light, scanning electron microscopy and mo-lecular approachs. M. lanfrediae sp. nov. presents the typical characteristics of the genus, but is morphometrically and morphologically different from the species described previously. The main diagnostic characteristics of M. lan-frediae sp. nov. are (i) seven pairs of regularly-distributed spherical papillae on the oral sucker, (ii) ventral sucker outlined by four pairs of papillae distributed in a uniform pattern and interspersed with numerous spines, which are larger at the posterior margin and (iii) small, rounded tegumentary papillae around the opening of the oral sucker, which are morphologically different from those of the oral sucker itself, some of which are randomly disposed in the ventrolateral tegumentary region of the anterior third of the body. Addionally, based on SSU rDNA, a phylogenetic analysis including Brachycoeliidae and Mesocoeliidae taxa available on GenBank established the close relationship between M. lanfrediae sp. nov. and Mesocoelium sp. The natural range of the cane toad, Rhinella marina (Linnaeus, 1758) (syn. Bufo marinus and Chaunus mari-nus) stretches from southern Texas to central Brazil. However, the species has also been introduced into a number of regions, such as Florida, Caribbean and Pa-cific islands, New Guinea and northwestern Australia, for the biological control of agricultural pests (Barton 1997, Ragoo & Omah-Maharaj 2003, Espinoza-Jiménez et al. 2007, Vallinoto et al. 2010). The family Mesocoeliidae Dollfus, 1929 (Digenea) is composed by parasites of the digestive organs of a num-ber of amphibian and reptile species including R. marina. This family has two genera: Mesocoelium Odhner, 1910 and Pintneria Poche, 1907 (Pojmanska 2008). This paper describes the morphological and molecular characteristics of a parasite of the genus Mesocoelium, which appear to be unique and have thus led us to propose a new species.