Piraeus is a port city within the Athens urban area, in the Attica region of Greece. It is located eight kilometres (5 mi) southwest of Athens' city centre along the east coast of the Saronic Gulf in the Athens Riviera.

The Saronic Gulf 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 Saronic Islands in the gulf have played a pivotal role in the history of Greece, with the largest, Salamis being the location of a significant naval battle in the Greco-Persian wars. The Megara Gulf makes up the northern end of the Saronic Gulf.