Gaius Julius Antiochus IV Epiphanes (Ancient Greek: Γάιος Ἰούλιος Ἀντίοχος ὀ Ἐπιφανής, before 17 AD – after 72 AD), the last king of Commagene, reigned between 38–72 as a client king to the Roman Empire. The epithet "Epiphanes" means "the Glorious".

Antiochus was born a prince of the royal family of Commagene. His parents King Antiochus III of Commagene and Queen Iotapa were full-blooded siblings who had married each other. The younger Antiochus himself would marry his full-blooded sister Iotapa. Antiochus was of Armenian,Greek and Median descent. Through his ancestor from Commagene, Queen Laodice VII Thea, who was the mother of King Antiochus I Theos of Commagene, he was a direct descendant of the Greek Seleucid kings.

Antiochus appears to have been very young when his father died in 17. The Roman emperor Tiberius agreed with the citizens of Commagene to make their kingdom a part of the Roman province of Syria. Between 17 and 38, Antiochus seems to have gained Roman citizenship. He lived and was raised in Rome, along with his sister. While he and his sister were growing up in Rome, they were part of the remarkable court of Antonia Minor, a niece of the first Roman emperor Augustus and the youngest daughter of the triumvir Mark Antony. Antonia Minor was a very influential woman and supervised her circle of various princes and princesses. Her circle assisted in the political preservation of the Roman Empire’s borders and affairs of the client states.

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