The Ionian League (ancient Greek: , Íones; , koinón Ionon; or , koine sýnodos Ionon; Latin: commune consilium), also called the Panionic League, was a confederation formed at the end of the Meliac War in the mid-7th century BC comprising twelve Ionian cities (a dodecapolis, of which there were many others). These were listed by Herodotus as

• Miletus, Myus, and Priene, all in Caria (a region in Asia Minor) and speaking the same dialect;
• Ephesus, Colophon, Lebedus, Teos, Clazomenae and Phocaea, in Lydia and-or the region known today as Ionia (both also in Asia Minor, Lydia extending inland much farther relative to Ionia), speaking another dialect;
• Chios (island) and Erythrae (Asia Minor), with a common dialect; and
• Samos (island), with its own dialect.

After 650 BC Smyrna, an originally Aeolic city, was invited to diminish Aeolis and increase Ionia by joining the league, which it did.