A native of Miletus, brother-in-law of Histiaeus, and left by the latter during his stay at the Persian court in charge of the government of Miletus. Having failed in an attempt upon Naxos (B.C. 501), which he had promised to subdue for the Persians, and fearing the consequences of his failure, he induced the Ionian cities to revolt from Persia. He applied for assistance to the Spartans and Athenians: the former refused, but the latter sent him twenty ships and [p. 126] some troops.

In 499 his army captured and burned Sardis, but was finally chased back to the coast. The Athenians now departed; the Persians conquered most of the Ionian cities; and Aristagoras in despair fled to Thrace, where he was slain by the Edonians in 497. (Harpers Dictionary of Classical Antiquities, 1898)