Saxifraga cataphracta, a new species of Saxifragaceae from Southwest China, is described and illustrated. Morphological and molecular evidence (matK, psbA-trnH, psaJ-rpl33) indicate that S. cataphracta belongs to S. sect. Irregulares, and closely related to S. geifolia and S. mengtzeana. The new species can be diagnosed by its leaf blade abaxially with white or virescent interveinal streaks, involucre and bracts conspicuous, capsule beaks winged when mature.