Antiochus I Soter (Greek: Ἀντίοχος Σωτήρ, Antíochos Sōtér; "Antiochus the Saviour"; c. 324/3 – 2 June 261 BC) was a Greek king of the Seleucid Empire. Antiochus succeeded his father Seleucus I Nicator in 281 BC and reigned during a period of instability which he mostly overcame until his death on 2 June 261 BC. He is the last known ruler to be attributed the ancient Mesopotamian title King of the Universe.