Coleostachys is a monospecific genus of Neotropical Malpighiaceae, known in the literature from only two collections. After a thorough analysis of Brazilian and International herbaria, we present a taxonomic revision of Coleostachys. This work includes a complete morphological description of the genus and its single species, C. genipifolia, along with line drawings and photograph plates, a distribution map, and comments on taxonomy, ecology and conservation of this obscure Amazonian genus.