(Uploaded by Plazi for the Bat Literature Project) We describe the first reported case of diphallia in a bat, Corynorhinus townsendii, captured during fall swarming at a hibernaculum in northern Utah, USA. Upon examination, we determined that one phallus was functional, as evidenced by production of urine, while the secondary phallus appeared to be overgrown with skin. A review of the medical literature relevant to diphallia suggests that this is a case of pseudodiphallia with a bifid shaft. We hypothesize that this morphological deformity likely has a low impact on the survival of this individual but may act as a physical barrier to copulation. To our knowledge, this is the first reported case of diphallia in bats.