Crotalaria trifoliolata Baker f. (Leguminosae: Papilionoidaeae) was, for 120 years, only known from an incomplete holotype from an uncertain Ethiopian locality. In 2013 it was rediscovered in the Bale Zone, eastern Ethiopia. Surveys in 2014 and 2015 suggest that the species is restricted to limestone habitats in the Kubayo National Forest, where it forms almost monospecific stands of up to one thousand individuals in glades and at forest margins. Predictive distribution models suggest uncertain suitability of the present habitats under future climatic conditions. Based on this and other potential threats, the species is evaluated as Endangered (EN). Crotalaria trifoliolata is a bigger shrub than previously thought (up to c. 2 m high, with stems up to c. 3 cm in diam.). Molecular studies confirm that C. trifoliolata is related to the widespread C. saltiana, as predicted from morphological observations. A later name, C. malacothcha Harms, is placed in synonymy of C. trifoliolata. Information from local informants suggests that Walenso, the name of the type locality for both C. trifoliolata and C. malacotricha, is a collective name for mountains within the Kubayo Forest.