Details are given of several morphological characters that separate the Vietnamese endemic Begonia balansana from the more widespread south Asian B. handelii, with which it is often confused. Begonia prostrata is reduced to a variety of B. handelii. Descriptions are provided for B. balansana and for B. handelii and the closely affiliated and poorly known B. burkillii. Begonia balansana is illustrated. Begonia handelii var. prostrata is recorded as new to Vietnam, Laos and Thailand and B. burkillii as new to Myanmar.