The Ionians (/aɪˈoʊniənz/; Greek: Ἴωνες, Íōnes, singular Ἴων, Íōn) were one of the four major tribes that the Greeks considered themselves to be divided into during the ancient period; the other three being the Dorians, Aeolians, and Achaeans. The Ionian dialect was one of the three major linguistic divisions of the Hellenic world, together with the Dorian and Aeolian dialects.
When referring to populations, “Ionian” defines several groups in Classical Greece. In the narrowest sense it referred to the region of Ionia in Asia Minor. In a broader sense it could be used to describe all speakers of the Ionic dialect, which in addition to those in Ionia proper also included the populations of Euboea, the Cyclades, and many cities founded by Ionian colonists. Finally, in the broadest sense it could be used to describe all those who spoke languages of the East Greek group, which included Attic.
The foundation myth which was current in the Classical period suggested that the Ionians were named after Ion, son of Xuthus, who lived in the north Peloponnesian region of Aegilaus. When the Dorians invaded the Peloponnese they expelled the Achaeans from the Argolid and Lacedaemonia. The displaced Achaeans moved into Aegilaus (thereafter known as Achaea), in turn expelling the Ionians from the Aegilaus. The Ionians moved to Attica and mingled with the local population of Attica, and many later emigrated to the coast of Asia Minor founding the historical region of Ionia.