Seleucus II, called Callinicus (circa 265-226 BC), ruler (247-226 BC) of the Seleucid kingdom, the son of Antiochus II Theos. Seleucus II was unable to prevent Ptolemy III of Egypt from invading Syria and Mesopotamia during the Third Syrian War (246-241 BC). He allowed the Bactrians and Parthians to establish their independence in the east and lost his possessions in Asia Minor to his brother Antiochus Hierax.