A new species of Cuora, Cuora chiangmuanensis sp. nov., is described on the basis of a nearly complete shell with limb bones from the late Middle – early Late Miocene Chiang Muan Mine, Phayao Province (Northern Thailand). C. chiangmuanensis is distinguished from other fossil and living Cuora species mainly on the basis of its plastral morphology. Among fossil and extant Cuora taxa, the new species appears to be a missing link between the taxa from Southeast Asia and those from East Asia. It represents the earliest record of the genus and demonstrates that by 11–12 Ma, Asian box turtles were already present in Southeast Asia.