Antiochus XII Dionysus (reigned 87–84 BC) was the fifth son of Antiochus VIII Grypus to take up the diadem, and succeeded his brother Demetrius III Eucaerus as separatist ruler of the southern parts of the last remaining Seleucidian realms, basically Damascus and its surroundings. He initially gained support from Ptolemaic forces but was killed in a campaign against the Nabataean Arabs, who conquered Damascus soon after.