| Phraates IV 𐭐𐭓𐭇𐭕 | |
|---|---|
| Great King, King of Kings, Arsaces | |
 Coin of Phraates IV, Mithradatkert mint | |
| King of the Parthian Empire | |
| Reign | 37–2 BC |
| Predecessor | Orodes II |
| Successor | Phraates V and Musa |
| Died | 2 BC |
| Spouse | Olennieire, Cleopatra, Baseirta, Bistheibanaps, Musa |
| Issue | Vonones I, Phraates, Seraspandes, Rhodaspes, Karen, Phraates V |
| Dynasty | Arsacid dynasty |
| Father | Orodes II |
| Religion | Zoroastrianism |
Phraates IV (also spelled Frahad IV; Parthian: 𐭐𐭓𐭇𐭕 Frahāt) was King of Kings of the Parthian Empire from 37 to 2 BC. He was the son and successor of Orodes II (r. 57–37 BC), and was given the throne after the death of his brother Pacorus I. Phraates IV soon murdered all his brothers, and also possibly his father. His actions alienated the Armenians and also some of his nobles, including the distinguished Monaeses, who fled to the Roman triumvir Mark Antony, but shortly returned and reconciled with Phraates IV.
Phraates IV was attacked in 36 BC by Mark Antony, who marched through Armenia into Media Atropatene, and was defeated and lost the greater part of his army. Antony, believing himself betrayed by Artavasdes II, king of Armenia, invaded his kingdom in 34 BC, took him prisoner, and concluded a treaty with Artavasdes I, king of Media Atropatene. But when the war with Octavian broke out, Antony could not maintain his conquests; Phraates IV recovered Media Atropatene and made Artaxias, the son of Artavasdes II, king of Armenia.
Around the same time, Phraates IV's throne was usurped by Tiridates II, but he quickly managed to reestablish his rule with the aid of Scythian nomads. Tiridates fled to the Romans, taking one of Phraates IV's sons with him. In negotiations conducted in 20 BC, Phraates IV arranged for the release of his kidnapped son. In return, the Romans received the lost legionary standards taken at Carrhae in 53 BC, as well as any surviving prisoners of war. The Parthians viewed this exchange as a small price to pay to regain the prince.
Along with the prince, Octavian (now known as Augustus) gave Phraates IV an Italian slave-girl named Musa, who quickly became queen and a favourite of Phraates IV, giving birth to Phraataces (Phraates V). Seeking to secure the throne for her son, Musa convinced Phraates IV to send his four first-born sons (Vonones, Phraates, Seraspandes and Rhodaspes) to Rome in order to prevent conflict over his succession. In 2 BC, Musa had Phraates IV poisoned and made herself along with Phraates V the co-rulers of the empire.