Phraates I (Parthian: 𐭐𐭓𐭇𐭕, romanized: Frahāt) was king of the Arsacid dynasty from 170/168 BC to 165/64 BC. He subdued the Mardians, conquered their territory in the Alborz mountains, and reclaimed Hyrcania from the Seleucid Empire. He died in 165/64 BC, and was succeeded by his brother Mithridates I (r. 165 – 132 BC), whom he had appointed his heir.