king of Parthia (reigned c. 138–128 BC), the son and successor of Mithradates I.

Phraates was attacked in 130 by the Seleucid Antiochus VII (Antiochus VII Sidetes) Sidetes, who after initial successes was defeated and killed during 129 in Media. With his defeat, Seleucid dominion over the countries east of the Euphrates River was finally ended. During these wars two powerful nomadic tribes, the Śakas and the Tocharoi, had forced their way into eastern Persia. Phraates advanced against them, pressing into service Greek prisoners from the army of Antiochus; but when the Greeks deserted him in battle, Phraates was defeated and slain. He was succeeded by his uncle Artabanus II.