The Strymon is a river in Bulgaria and Greece.
Called Strimon in Greek, Struma in Bulgarian, and Karasu in Turkish. Rises in the Vitosha Mountains of Bulgaria and flows about 400 kilometers south to the Aegean Sea. The valley is a coal-producing area of Bulgaria. The ancient Greek city of Amphipolis was founded at the river's entrance to the Aegean, and the Battle of Kleidion was fought by the river in 1014.