Amarynthos (Greek: Αμάρυνθος, , also called Βάθεια Váthia), is a coastal town and a former municipality in Euboea, Greece. Since the 2011 local government reform it is part of the municipality Eretria, of which it is a municipal unit. In 2001 its population was 4,141 for the town and 7,356 for the municipal unit. The Amarynthos is 8 km east of Eretria, 27 km southeast of Chalcis, 63 km northwest of Karystos and 10 km north of Kalamos, across the gulf. The Greek National Road 44 (Thebes - Chalcis - Karystos) passes through the town.