A new monogenean fluke, collected from the urinary bladder of a megophryid frog, Xenophrys glandulosa Fei, Ye & Huang, 1991 from Mokokchung and Tuensang districts of Nagaland, north-eastern India is described. Of the six genera under the subfamily Polystomatinae (Polystomatidae) known so far, the present form comes closer to Eupolystoma Kaw, 1950; Pseudopolystoma Yamaguti, 1963 and Riojatrema Lamothe-Argumedo, 1964, in all of which the opisthaptor lacks large hooks. However, a combination of characters, namely, shape of the body, rounded or bulbous pharynx, intestinal caeca not joining posteriorly in the opisthaptoral region, ovary located in the anterior third of the body and presence of vaginal apertures, sets the present form apart from all these genera, and also from the known species of Riojatrema. These differences warrant the establishment of a new species and a new genus to accommodate the present form. The validity of this new monogenean, named as Neoriojatrema mokokchungensis after the type locality of the fluke, is discussed.