Amarynthos, 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. The municipal unit has an area of 109.909 km2. In 2011 its population was 3,672 for the town and 6,723 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 passes through the town.