Elefsina or Eleusis is a suburban city and municipality in Athens metropolitan area. It belongs to West Attica regional unit of Greece. It is located in the Thriasio Plain, at the northernmost end of the Saronic Gulf. North of Elefsina are Mandra and Magoula, while Aspropyrgos is to the northeast.

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.