TheBegonia longifolia Blume complex is revised and seven species are recognized.Begonia crassirostris Irmsch.,B. inflata C. B. Clarke,B. tricornis Ridl., andB. trisulcata (A. DC.) Warb. are synonymized withBegonia longifolia Blume, making this the most widely distributedBegonia species within Asia.Begonia tetragona Irmsch. is synonymized withB. acetosella Craib. Descriptions are provided forBegonia longifolia, B. acetosella, and four closely related and also poorly known species with baccate fruit:B. cristata Warb. ex L. B. Sm. & Wassh.,B. renifolia Irmsch.,B. sarcocarpa Ridl., andB. turbinata Ridl.Begonia hayatae Gagnep. is also recognized as a member of this complex but is not described here. Evidence for a speciation mechanism within this group is discussed.Begonia acetosella andB. sarcocarpa are lectotypified.