Lake Trichonida, also Trihonida is the largest natural lake in Greece. It is located in the eastern part of the Aitoloakarnania prefecture, in the east of Agrinio, south of Evrytania and northwest of Nafpaktos. It covers an area of 98.6 square kilometres (38.1 sq mi) with a maximum length of 19 kilometres (12 mi) and maximum depth of 58 metres (190 ft).
One million years ago the lake was large enough to cover the central part of Aitoloakarnania, a part that is now a plain. The lake later dried up and today is located in the east-central portion of the prefecture. The municipalities with shores on the lake are Thermo, Makryneia, Arakynthos, Thestieis, and Paravola. Around the lake, there are beautiful forests with maples, pines and other trees. The lake and its environs is home to more than 200 birds. There are also farmland and various villages surrounding the area.