Cyananthus Wallich ex Bentham, the only genus of Campanulaceae with superior ovary, is revised to clarify infrageneric relationships and phylogeny of the genus. Evidence obtained from the comparative gross morphology, anatomy, palynology, and karyomorphology recommends a new infrageneric classification of the genus, recognizing 23 species, belonging to two subgenera, four sections and four subsections. One subgenus(Subgen. Micranthus), one section(Sect. Suffruticulosi) and two subsections(Subsect. Flavi and Subsect. Lichiangenses)are described as new taxa. New combinations at sectional(Sect. Annui) and subsectional(Subsect. Stenolobi) ranks are also proposed. The genus Cyananthus is strictly distributed in the high mountains of China(Xizang, Yunnan and Sichuan), extending to Bhutan, Nepal and India(Kumaon-Garhwal, Assam and Sikkim), with altitudinal ranges from 2500～5300 m. It is observed that 13 species are endemic to SW China and only three species are endemic to the Himalayas(two species in Nepal and one to NW India). It is evident that Cyananthus is one of the most primitive genera of Campanulaceae and within the genus, subgenus Cyananthus(Sect. Stenolobi) is more primitive than the subgenus Micranthus. It is also suggested that SW China(most probably Yunnan) is the center of origin of Cyananthus, considering the occurrence of as many as 20 species of Cyananthus, representing several primitive taxa and many endemic species.