The Ionian League (Ancient Greek: Ἴωνες, romanized: Íōnes; κοινὸν Ἰώνων, koinón Iōnōn; or κοινὴ σύνοδος Ἰώνων, koinē sýnodos Iōnōn, in 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[2] comprising twelve Ionian Greek city-states (a dodecapolis, of which there were many others), and eventually thirteen city-states with the admission of Smyrna.
The twelve ancient city-states were listed by Herodotus as:[3] Smyrna, an originally Aeolic city bordering the Ionians, asked for admission and entered the League at a later date, being first attested in a decree of 289/8 BC.
[4] The league is still attested as having thirteen members as late as the 3rd century AD, but this may reflect tradition more than reality, as due to synoecisms and the fluctuation in importance of the various cities, some were incorporated into others over time (e.g. Myus became part of Miletus).
[5] One of the earliest known historical sources, the Histories of Herodotus, and early inscriptions refer to the legally constituted body customarily translated by "league" as "the Ionians" in the special sense of the cities incorporated by it.
Writers and documents of the Hellenistic Period explicitly use the term koinon ("common thing") or synodos ("synod") of the Ionians, and by anachronism apply it to the early league when they mention it.