The Aheloy River (Bulgarian: Ахелой) or Achelous (Greek: Αχελώος) is a river in eastern Bulgaria. It originates in the Aytos-Karnobat mountain, 1.5 kilometres from Dryankovets, and flows directly into the Black Sea south of the village of Aheloy. The Aheloy River has a length of 39.9 kilometres and has an irrigation reservoir, the Aheloy Reservoir, built along its flow. The river's drainage basin covers 141 square kilometres and its average discharge is 0.7 cubic metres per second.