Begonia grandis Dry. (Begoniaceae), previously recognized as endemic to continental China, was recently discovered from southern Taiwan. Close morphological observations and molecular phylogenetic analysis elucidated that the species in Taiwan belongs to subspecies grandis. Begonia grandis has a long history in cultivation especially in China and Japan but not in Taiwan. The collection locality in Taiwan had no trace of human activity. Therefore, B. grandis is considered to be native to Taiwan. The new finding in Taiwan marks the southernmost distribution record of the species. Unfortunately, the discovered population was destroyed by a landslide due to a typhoon in 2009. Further field survey in neighboring areas is needed to elucidate the current status of B. grandis in Taiwan.