Parthamasiris, also known as Partamasir or Parthomasiris (flourished second half of the 1st century and first half of the 2nd century, died 114) was a Parthian prince who served as a Roman client king of Armenia.
Parthamasiris was one of the three sons born to King Pacorus II of Parthia by a mother whose name is unknown. Through his father he was a member of the House of Parthia thus a relation of the Arsacid dynasty of Armenia. Little is known of his life prior to becoming Armenian king.
In 113, Parthamasirisâ paternal uncle Osroes I of Parthia deposed his brother Axidares from the Armenian kingship and installed him as king to avoid to going to war with the Roman emperor Trajan and keep peace with him. Axidares was placed on the Armenian throne by his paternal uncle without Roman consultation which led to Trajan to view the action by Osroes I as an invitation to war with Parthia.
In 114, the Roman army invaded Armenia from Satala and advanced toward Artaxata. Unable to organize an effective resistance, Parthamasiris appeared before Trajan. In a symbolic gesture, Parthamasiris removed his crown and placed it at the Emperor's feet, expecting to have it restored to him. After rejecting Parthamasirisâ request, Trajan annexed Armenia as a Roman province.
Trajan sent Parthamasiris from Armenia back home to Parthia and continued on with his Parthian military campaign. On his way home to Parthia, Parthamasiris disappeared; historian David Bivar has speculated that Trajan may have ordered Parthamasiris's murder.
No coinage bearing the image of Parthamasiris was minted in Armenia; however, his likeness was captured on several Roman imperial issues. In Roman numismatics, Parthamasiris is frequently depicted alongside the Emperor Trajan to emphasize the latter's supremacy. The first series of these coins illustrates the encounter between Trajan and Parthamasiris: the Emperor is represented in a triumphant and dominant posture upon a raised tribunal, while Parthamasiris is positioned below him. This iconography was intended to symbolize Roman dominion, Trajan's military might, and the Emperor's administrative control over the region.