The first stag beetle from the Upper Cretaceous Burmese amber is described and figured. Protonicagus tani gen. et sp. nov. is firmly placed in the extant lucanid subfamily Aesalinae based on the narrow prosternal process, the non-geniculate antenna, and the pronotal and elytral vestiture with conspicuous scales. Protonicagus tani represents the first fossil record for the tribe Nicagini. Along with the modern disjunctive distribution pattern of the closely related Nicagus LeConte in the North America and Japan, our discovery indicates that Nicagini are probably an ancient group, and they were widespread at least in Laurasia before the continent eventually broke up.