We report the discovery of a new species of Lophostoma from Panama, which we name L. kalkoae. This new species resembles L. carrikeri and L. yasuni in possessing a white venter, but is distinguishable from both by external and cranial characteristics. The new species is similar in size to L. carrikeri and L. schulzi. Lophostoma sp. nov. can be most easily recognized by its combination of white venter, postauricular patches connected by a thin line of pale hair to the white fur on the chest, elongated clitoris and swollen labia, less strongly developed lateral projection of mastoid processes, well-marked indentation on the lingual cingulum of the upper canine, well-developed P3, well-developed posterior lingual cusp on the cingulum of P4, and parastyle absent on M1 and M2. We present a dichotomous key for the genus Lophostoma and a map showing all the localities where white-bellied Lophostoma have been recorded.