A newly discovered, third species of the genus Lamproptera (Lepidoptera: Papilionidae) is described, 183 years after the second currently recognised species was first named. Lamproptera paracurius Hu, Zhang & Cotton sp. n., from N.E. Yunnan, China, is based on marked differences in external morphology and male genital structure. The species is confirmed as a member of the genus, and detailed comparisons are made with other taxa included in the genus. Keys to Lamproptera species based on external characters and male genitalia are included.