Potorostrongylus woyliei sp. n. (Nematoda: Cloacinidae), a new nematode from the stomach of the brush-tailed bettong Bettongia penicillata is described and a revised key to the genus provided. The new species most closely resembles Potorostrongylus finlaysoni Johnston and Mawson, 1939 and Potorostrongylus temperatus Smales, 1997 but differs from both in the shape of the submedian lips, the length of the spicules, and the proportions of the elements of the ovejector. Each potoroid host species is associated with a particular species of Potorostrongylus, suggesting coevolution of host and helminth. Additional potoroid–potorostronglyid associations appear to be incidental infections resulting from sympatric host distribution.