Bakırçay (Latin name: Caicus, also Caecus; Greek: Καϊκός, transliterated as Kaïkos; formerly Astraeus) is the current name of a river of Asia Minor that rises in the Temnus mountains and flows through Lydia, Mysia, and Aeolis before it debouches into the Elaitic Gulf. To the Hittites, it may have been the Seha river, however the modern Gediz river further south is a more likely candidate.