Antiochus I (Antiochus Soter) (āntī´əkəs sō´tər), b. c.324 BC, d. c.262 or 261 BC, king of Syria (280–261? BC), son of Seleucus I. He did not, like his father, seek to expand in Europe. The Seleucid holdings were greatly reduced, particularly by the Egyptians under Ptolemy II. Antiochus was famous as a founder of cities.