The Saronic Gulf or Gulf of Aegina in Greece forms part of the Aegean Sea and defines the eastern side of the isthmus of Corinth. It is the eastern terminus of the Corinth Canal, which cuts across the isthmus. Islands that are lined in the middle of the Gulf are Aegina, Salamis, and Poros. The Port of Piraeus, also Athens' port is lying on the northeastern edge of the gulf. Ellinikon International Airport, used to stood is also in the northeast. Beaches are lined up to much of its coast from Poros to Epidaurus, Loutra Elenis to Kineta and from Megara to Eleusis and from Piraeus down to Anavysso. Athens' urban area surrounds the northern and the eastern coasts of this gulf.

Tributaries