Eupolystoma vanasi is described as a new species of the Polystomatidae parasitic in the urinary bladder of Schismaderma carens in Northern Province and KwaZulu-Natal Province, South Africa. This is the third Eupolystoma species described from Africa and the first polystomatid from Schismaderma, an anuran genus that is primitive with respect to the other African bufonids in which Eupolystoma has been recorded. The species is distinguished by body size (this is the largest Eupolystoma known; mean length of adults 6 mm), by genital spine number (4 in comparison with 6-9 in other species), marginal hooklet length (greater than in other African species), and by the small size of the ovary and testis. In a sample of 27 toads, 37% were infected with up to 130 parasites per host (mean intensity 37). Worm burdens of this magnitude are exceptional amongst polystomatids in general but are characteristic of Eupolystoma, where there may be repeated re-infection of adult hosts and, uniquely, a direct, internal cycle of auto-infection.