The Neotropical bat genus Platyrrhinus (Chiroptera: Phyllostomidae: Stenodermatinae) currently comprises 15 species. Our morphological and morphometric analysis of large and medium-sized Platyrrhinus revealed a distinctive undescribed species from western South America. We also recognize P. aquilus (Handley & Ferris 1972) and P. umbratus (Lyon 1902) as valid species. We describe P. nitelinea sp. nov. from western Colombia and Ecuador and provide emended diagnoses along with descriptions of P. aquilus, P. dorsalis, and P. umbratus. Phylogenetic analysis of Platyrrhinus based on morphological characters indicates that P. aquilus is closely related to P. aurarius and P. nigellus, P. umbratus to P. chocoensis, and P. nitelinea to P. vittatus.