Ariobarzanes III Eusebes Philorhomaios: King of Cappadocia and Rome’s Ally

Introduction

Ariobarzanes III Eusebes Philorhomaios was king of Cappadocia from about 51 to 42 BC. A son of Ariobarzanes II and of mixed Persian and Greek descent, he was confirmed as his father’s successor with the assent of the Roman Senate. Cicero, then proconsul of Cilicia, records that the young king’s court was factional and that conspiracies, including one involving the powerful priest‐ruler Archelaos of Comana and a plot to place his brother on the throne, required Roman intervention to suppress.

During the Roman civil wars Ariobarzanes aligned with Pompey’s eastern client rulers but remained in office after Julius Caesar’s victory; Caesar temporarily awarded him part of Lesser Armenia (about 47–44 BC), and sources record his cooperation with Roman generals during regional fighting—he supported Roman efforts against Pharnakes II of Pontus, whose advance briefly imperiled Cappadocia. The king carried heavy obligations to prominent Romans, which complicated his rule.

In 42 BC Cassius Longinus had Ariobarzanes executed after accusing him of failing to support the conspirators against the Caesarian party; his possessions were plundered and he was succeeded by his brother Ariarathes X. His epithet Eusebes Philorhomaios and surviving accounts portray him as a pro‐Roman monarch whose reign was defined by dependence on Rome, internal court rivalries, and the shifting allegiances of the late Republic.