Thermo (Greek: Θέρμο, before 1915: Κεφαλόβρυσον - Kefalovryson) is a town and a municipality in Aetolia-Acarnania, Greece. It is located in the southeastern part of the regional unit, largely between Lake Trichonida (the largest natural lake in Greece) and the southern border of Evrytania. It has a land area of 333.701 km2 (129 sq mi) and a population of 8,242 inhabitants (2011 census).
Its municipal seat is the town of Thermo (pop. 1,959). Its largest other towns are Analipsis (pop. 734), Petrochori (444), Sitaralona (664), Myrtea (729), and Koniska (326). The nearby village of Mega Dendron was the birthplace of Cosmas of Aetolia.
Thermo took its name from the ancient city Thermos, that was located near the present town.