Nafpaktos (Ναύπακτος) is a town and a former municipality in Aetolia-Acarnania, West Greece, situated on a bay on the north coast of the Gulf of Corinth, west of the mouth of the river Mornos.
It is named for Naupaktos (Ναύπακτος, Latinized Naupactus), an important Athenian naval station in the Peloponnesian war. As a strategically crucial possession controlling access to the Gulf of Corinth, Naupaktos changed hands many times during the Crusades and the Ottoman–Venetian Wars. It was under Venetian control in the 15th century, and came to be known by the Venetian form of its name, Lepanto. It fell to the Ottoman Empire in 1499 and was used as naval station by the Ottoman Navy in the 16th century, being the site of the decisive victory by the Holy League in the Battle of Lepanto in 1571. Except for a brief period of Venetian control in 1687–1699, Lepanto remained under Ottoman control until Greek independence in 1829.
The modern municipality was incorporated in 1946, and later merged into the larger Nafpaktia municipality in the 2010 reform. Nafpaktos is now both the name of a municipal unit within Nafpaktia and of the town proper within the Nafpaktos unit.
The municipal district has an area of , with a population close to 20,000 .
The town is northeast of Antirrio, northeast of Patras, east of Missolonghi and southeast of Agrinio. The Greek National Road 48/E65 (Antirrio – Nafpaktos – Delphi – Livadeia) passes north of the town. It is the second largest town of Aetolia-Acarnania, after Agrinio.
The ancient name Naupaktos (Ναύπακτος) means "boatyard" (from ναύς naus "ship" and πήγ- pêg- "to fix, fasten"). It was later Latinized as Naupactus. By the late medieval period, the local name had evolved into Nepahtos (Νέπαχτος), Epaktos or Epahtos (Έπακτος, Έπαχτος). By the "Franks" (Latins) it was called Neopant, Nepant or Lepant. French sources of the 14th century give Nepant or Neopant; Venetian sources have Nepanto or Lepanto.
The name was adapted in Ottoman Turkish from Greek Νέπαχτος as Aynabahti or İnebahtı.