born 323 BC; died 261, son of Seleucus Nicator. He fell in love with his stepmother, Stratonike, and became very ill. His father, when he discovered the cause of his son’s illness, gave her to him in 293, and yielded to him the sovereignty over all the countries beyond the Euphrates, as well as the title of king. When Seleucus returned to Macedonia in 281, he was murdered by Ptolemeus Ceraunus. Antiochus thus became ruler of the whole Syrian kingdom. He waged war on Eumenes of Pergamum, but without success. For the victories of his elephant corps over the Gauls, who had settled in Asia Minor, he received the surname of Soter ("Deliverer"). It was in a battle with these inveterate foes of his country that he met his death (261 BC). See also SELEUCIDAE.