Acarnania is a region of west-central Greece that lies along the Ionian Sea, west of Aetolia, with the Achelous River for a boundary, and north of the gulf of Calydon, which is the entrance to the Gulf of Corinth. Today it forms the western part of the regional unit of Aetolia-Acarnania. The capital and principal city in ancient times was Stratos. The north side of Acarnania of the Corinthian Gulf was considered part of the region of Epirus.