The present study sheds light on species delimitation in what has been previously described as Rhinolophus arcuatus, a morphologically conservative bat species complex nominally distributed throughout archipelagic South-East Asia from New Guinea to Sumatra. Given that rhinolophids tend to be relatively weak fliers, hence have low vagility, we hypothesized that some specimens attributed to R. arcuatus, but originating from geographically disjunct populations, may in fact represent distinct species. To test this hypothesis, we examined specimens attributed to R. arcuatus as well as to other species in the Rhinolophus euryotis species group using both morphological techniques and mitochondrial cytochrome b and control region sequences. Careful morphological analysis reveals heretofore cryptic but nevertheless distinct, species-level morphological differences among specimens derived from geographically isolated locations. Furthermore, molecular data illuminate the existence of several species-level sequence divergences among specimens heretofore attributed to R. arcuatus. These analyses similarly suggest the existence of additional species in other South-East Asian Rhinolophus taxa previously considered monotypic. We suggest at least one description to be undertaken of a previously unrecognized species as well as the elevation of several others from sub-specific to specific status.