Several lines of evidence (morphological, karyological and molecular) support the exclusion of both Sebaea madagascariensis Klack. and S. condensata Klack. from Sebaea Sol. ex. R. Br. (Gentianaceae - Exaceae), resulting in the establishment of a new genus Klackenbergia Kissling and two new species combinations: K. stricta (Schinz) Kissling (= S. madagascariensis) and K. condensata (Klack.) Kissling. Klackenbergia is endemic to Madagascar and is morphologically recognized by its inflorescence with long bracts and bracteoles and subsessile flowers arranged in axillary fascicules at each node. Affinities with the other genera of the tribe Exaceae (Exacum, Gentianothamnus, Ornichia, Sebaea, Tachiadenus) are discussed.