Phocaea, or Phokaia, (Greek: Φώκαια) (modern-day Foça in Turkey) was an ancient Ionian Greek city on the western coast of Anatolia. Greek colonists from Phocaea founded the colony of Massalia (modern day Marseille, in France) in 600 BC, Emporion (modern day Empúries, in Catalonia, Spain) in 575 BC and Elea (modern day Velia, in Campania, Italy) in 540 BC.

Phocaea was the northernmost of the Ionian cities, on the boundary with Aeolis. It was located near the mouth of the river Hermus (now Gediz), and situated on the coast of the peninsula separating the Gulf of Cyme to the north, named for the largest of the Aeolian cities, and the Gulf of Smyrna (now İzmir) to the south.

Phocaea had two natural harbours within close range of the settlement, both containing a number of small islands. Phocaea's harbours allowed it to develop a thriving seafaring economy, and to become a great naval power, which greatly influenced its culture.^{[citation needed]}

Recent archaeological surveys have shown that the city of Phocaea was large for the archaic period. Herodotus gives an idea of the size of Phocaea by the describing the walls of Phocaea as having a diameter of 5 km, large even by modern standards. Phocaea was one of the largest cities in the ancient world.^{[citation needed]}