Missolonghi or Mesolongi is a municipality of 32,048 people in western Greece. The town is the capital of Aetolia-Acarnania regional unit, and the seat of the municipality of Iera Polis Mesolongiou. Missolonghi is known as the site of a dramatic siege during the Greek War of Independence, and of the death of poet Lord Byron.

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.