Byasa rhadinus is a species of butterfly from the family Papilionidae. It is found in China.
Originally described as Papilio mencius Felder, 1862 subsp. rhadinus Jordan, 1928, this butterfly was considered conspecific with Atrophaneura mencius (e.g., Collins & Morris 1985, Fujioka et al. 1997). It has been reclassified as a viable species by Chou (1994).