| Phraates III 𐭐𐭓𐭇𐭕 | |
|---|---|
| Great King King of Kings Arsaces | |
 | |
| King of the Parthian Empire | |
| Reign | 69 – 57 BC |
| Predecessor | Sinatruces |
| Successor | Mithridates IV |
| Died | 57 BC |
| Spouse | Piriustana, Teleuniqe |
| Issue | Mithridates IV Orodes II unnamed daughter |
| Dynasty | Arsacid dynasty |
| Father | Sinatruces |
| Religion | Zoroastrianism |
Phraates III (also spelled Frahad III; Parthian: 𐭐𐭓𐭇𐭕 Frahāt), was King of Kings of the Parthian Empire from 69 BC to 57 BC. He was the son and successor of Sinatruces (r. 75–69 BC).
At Phraates III's accession, his empire could no longer be considered the supreme power in the Near East, because of the ascendancy of Armenia under Tigranes the Great (r. 95–55 BC) and Pontus under his ally Mithridates VI Eupator (r. 120–63 BC). Phraates III's reign was thus marked by his efforts to restore his empire to its former position. To the west of his empire, war had engulfed the area. Tigranes and Mithridates VI urged him to join their war against the Roman Republic, while the Romans tried in turn to convince Phraates III to join them. Phraates III seemingly made promises to both parties but remained passive. He awaited the outcome of the war to take advantage of it at the right moment for the Parthians.
In 65 BC, Phraates III and his new son-in-law Tigranes the Younger (who was Tigranes the Elder's son) led an expedition into Armenia. Initially successful, their efforts were halted by a long siege at Artaxata. This led Phraates III to put Tigranes the Younger in charge of the Armenian expedition, reinforcing him with some Parthian soldiers. Tigranes the Younger, however, was ultimately defeated by his father, leading him to desert Phraates III and join the Roman commander Pompey instead. Tigranes the Elder soon submitted to the Romans who kept him as king. They appointed Tigranes the Younger the ruler of Sophene. However, he quickly fell out with Pompey and was sent as a prisoner to Rome. This was contested by Phraates III but to no avail.
Around the same time—in late 65 BC—Phraates III reconquered Adiabene, Gordyene and northern Mesopotamia from Tigranes. However, a Roman attack under the generals Aulus Gabinius and Lucius Afranius as far as the Tigris resulted in Phraates III losing Gordyene, which was restored to Tigranes by the Romans. At the start of 64 BC, while Pompey was focusing on his expedition against Mithridates VI, Phraates III invaded Armenia, and ultimately reached an accord with Pompey and Tigranes; Mesopotamia and Adiabene were confirmed as Parthian territory, while Gordyene was confirmed as Armenian. Furthermore, a peace treaty was concluded between Phraates III and Tigranes.
In c. 57 BC Phraates III was murdered by his two sons, Orodes II and Mithridates IV, with the latter ascending the throne. A civil war between the two brothers soon erupted and Orodes II emerged victorious.