The Gulf of Corinth or the Corinthian Gulf is a deep inlet of the Ionian Sea separating the Peloponnese from western mainland Greece. It is bounded in the east by the Isthmus of Corinth which includes the shipping route of the Corinth Canal, and in the west by the Strait of Rion, which separates the Gulf of Corinth from the outer Gulf of Patras at Cape Drepano, where the narrowest point is crossed by the Rio-Antirio bridge. The Gulf of Corinth is almost surrounded by the prefectures of Aetolia-Acarnania, Phocis in the north, Boeotia in the northeast, Attica in the east, Corinthia in the southeast and south and Achaea in the southwest. The gulf is one of the most seismic regions in Europe.
In medieval times, the gulf was known as the Gulf of Lepanto. Here the third Battle of Lepanto was fought in 1571, destroying the Ottoman fleet. In 1772 another Turkish fleet was destroyed by the Russians at the entrance to the gulf. The town of Lepanto is now named Naupactus.
The shipping routes between Athens and to the ports of the rest of the world including the Mediterranean ports pass along this gulf. Ferry routes link Aigio and Agios Nikolaos in the western part of the gulf.
The cities and towns that lie next to the gulf are: