Messapia (Greek: Μεσσάπια) is a former municipality in Euboea, Greece. Since the 2011 local government reform, it is part of the Dirfys-Messapia municipality, of which it is a municipal unit. The municipal unit has an area of 433.26 km and a population of 12,048 (2021). Its name derives from the ancient river Messapios, which flows through the middle of the island. The seat of the municipality was in Psachna.