Pterospermum mengii P.Wilkie (Dombeyoideae, Malvaceae/Sterculiaceae) from Cambodia and Vietnam is described as new to science and illustrated. It is most similar to Pterospermum pecteniforme Kosterm., sharing a distinctive wavy ridge at the margin of each locule of the capsular fruit, but differing by its larger leaves, oblong to obovate leaf shape, deeply cordate leaf base, and stellate indumentum on the undersurface of the leaves and fruit.