Four species of Mastigostyla (Iridaceae) from Bolivia are described, illustrated and maps of their distribution provided: M. cardenasii R. C. Foster, M. chuquisacensis Huaylla & Wilkin, M. torotoroensis Huaylla & Wilkin and M. woodii Huaylla & Wilkin, the last three as new species. Mastigostyla gracilis R. C. Foster is synonymised under M. cardenasii R. C. Foster. Notes on conservation status, nomenclature and identification are included. Although some uncertainty exists over generic placement due to phylogenetic systematic research now in progress, marked infraspecific variation is documented for the first time within South American Tigridieae. This draws attention to the need for more extensive sampling if adequate species delimitation is to be achieved in Tigridieae. Photographs illustrate morphological variation in all four species. A key is provided to facilitate identification of Bolivian Mastigostyla. © 2010 The Board of Trustees of the Royal Botanic Gardens, Kew.