Antiochus (//; Greek: Ἀντίoχoς; killed c. 226 BC), called Hierax (//, Ἱέραξ, "Hawk") for his grasping and ambitious character, was the younger son of Antiochus II and Laodice I and separatist leader in the Hellenistic Seleucid kingdom, who ruled as king of Syria during his brother's reign.
On the death of his father, in 246 BCE, Antiochus waged war on his brother Seleucus II Callinicus, in order to seize Anatolia for himself as an independent kingdom. He defeated his brother at the Battle of Ancyra in ca. 239 BC. But Antiochus was ultimately laid low, chiefly through the efforts of Attalus, king of Pergamon, who defeated him at the Battle of the Harpasus and drove him out of Anatolia. Antiochus subsequently fled to Egypt where he was killed by robbers in c. 226 BC.
- Plutarch, Sayings of Kings and Commanders, p.184; On Brotherly Love, p.489
- Overtoom, "The Power-Transition Crisis of the 240s BCE and the Creation of the Parthian State," The International History Review Volume 38, 2016 - Issue 5. Pages 984-1013. 
- Justin, Epitome of Pompeius Trogus, xxvii. 2-3; Polyaenus, Stratagemata, iv. 17; Eusebius, Chronicon (Schoene ed.), pag. 251; Pompeius Trogus, Prologi, 27;
- William Smith, ed. (1867) . ""Antiochus Hierax"". Dictionary of Greek and Roman Biography and Mythology. 1. Boston: Little, Brown, and Co. p. 194. Retrieved 23 September 2010.
- Antiochus Hierax, article in historical sourcebook by Mahlon H. Smith
- Antiochus Hierax, list of sources at attalus.org
This article incorporates text from a publication now in the public domain: Smith, William, ed. (1870). "article name needed". Dictionary of Greek and Roman Biography and Mythology.