Thermo (, 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 and a population of 8,242 inhabitants (2011 census).