Agrinio is the largest city of the Aetolia-Acarnania regional unit of Greece and its largest municipality, with 89,691 inhabitants (2021). It is the economic center of Aetolia-Acarnania, although its capital is the town of Mesolonghi. The settlement dates back to ancient times. Ancient Agrinion was 3 kilometres northeast of the present city; some walls and foundations of which have been excavated. In medieval times and until 1836, the city was known as Vrachori (Βραχώρι).

Aetolia-Acarnania is one of the regional units of Greece. It is part of the geographic region of Central Greece and the administrative region of West Greece. A combination of the historical regions of Aetolia and Acarnania, it is the country's largest regional unit. Its capital is Missolonghi for historical reasons, with its biggest city and economic centre at Agrinio. The area is now connected with the Peloponnese peninsula via the Rio-Antirio Bridge. The surrounding regional units take in Arta in Epirus, a narrow length bordering Karditsa of Thessaly, Evrytania to the northeast, and Phocis to the east.