Begonia locbaosangii from Lang Son Province is described and illustrated. In its variegated leaves with palmate venation, 4-tepalled staminate flowers and 3-tepalled pistillate flowers, B. locbaosangii somewhat resembles B. yizhouensis, a species endemic to the subtropical limestone area of Guangxi, China, but it is distinct from B. yizhouensis by its stipule margin entire (vs densely white ciliate), lamina upper surface very sparsely minutely scabrescent (vs glabrous), anthers apex rounded (vs retuse) and axile placentation (vs parietal placentation). Among Vietnamese begonias, it is most similar to B. jubar in its rhizomatous habit, patterns of variegated leaves and the number of both staminate and pistillate tepals, but it is different from the latter in its glabrous (vs densely hirsute) rhizome, leaves sparsely minutely scabrescent (vs glabrous) adaxially, ovary wings crescent-shaped (vs triangular) and undivided placentae lamellae (vs bilamellate). According to the IUCN Red List Categories and Criteria (Version 15), B. locbaosangii is assessed to be Data Deficient (DD).