The Saronic Gulf (Greek: Σαρωνικός κόλπος, Saronikós kólpos) or Gulf of Aegina in Greece is formed between the peninsulas of Attica and Argolis and forms part of the Aegean Sea. It defines the eastern side of the isthmus of Corinth, being the eastern terminus of the Corinth Canal, which cuts across the isthmus.
The gulf includes the islands of Aegina, Salamis, and Poros along with smaller islands of Patroklos and Fleves. The port of Piraeus, Athens' port, lies on the northeastern edge of the gulf. The site of the former Ellinikon International Airport is also in the northeast.
Beaches line much of the gulf coast from Poros to Epidaurus, Galataki to Kineta and from Megara to Eleusis and from Piraeus down to Anavyssos. Athens' urban area surrounds the northern and the eastern coasts of this gulf.
Bays in the gulf include Phaleron Bay, Elefsina Bay to the north, Kechries Bay in the northwest and Sofiko Bay in the east.
The volcano of Methana is located to the southwest along with Kromyonia at the Isthmus of Corinth, Aegina and Poros. Methana is also the youngest most active volcano center and forms the northwestern end of the cycladic arch of active volcanoes that includes Milos island, Santorini island and Nisyros island. A hydropathic institute at Methana makes use of the hot sulphurous water that still surfaces in the area. The most recent eruption was of a submarine volcano north of Methana in the 17th century.