Son of the preceding, and surnamed Nicator (Νικάτωρ), or "the Conqueror." He drove out Alexander Balas, with the aid of Ptolemy Philometor, who had given him his daughter Cleopatra in marriage, though she was already the wife of Balas. He ascended the throne B.C. 146, but soon abandoned himself to a life of indolence and debauchery, leaving the reins of government in the hands of Lasthenes, his favourite, an unprincipled and violent man. The disgust to which his conduct gave rise induced Tryphon, who had been governor of Antioch under Balas, to revolt, and place upon the throne Antiochus Dionysius, son of Balas and Cleopatra , a child only four years of age. A battle ensued, in which Demetrius was defeated, and Antiochus, now receiving the surname of Theos, was conducted by the victors to Antioch and proclaimed king of Syria. He reigned, however, only in name. The actual monarch was Tryphon, who put him to death at the end of about two years and caused himself to be proclaimed in his stead. Demetrius, meanwhile, held his court at Seleucia. Thinking that the crimes of Tryphon would soon make him universally detested, he turned his arms in a different direction and marched against the Parthians, in the hope that, if he returned victorious, he would be enabled the more easily to rid himself of his Syrian antagonist. After some successes, however, he was entrapped and made prisoner by the Parthian monarch Mithridates, and his army was attacked and cut to pieces. His captivity among the Parthians was an honourable one, and Mithridates made him espouse his daughter Rhodoguna. The intelligence of this marriage so exasperated Cleopatra that she gave her hand to Antiochus Sidetes, her brotherin-law, who thereupon ascended the throne. Sidetes having been slain in a battle with the Parthians after a reign of several years, Demetrius escaped from the hands of Mithridates and resumed the throne. His subjects, however, unable any longer to endure his pride and cruelty, requested from Ptolemy Physcon a king of the race of the Seleucidae to govern them. Ptolemy sent Alexander Zubinas. Demetrius, driven out by the Syrians, came to Ptolemaïs, where Cleopatra , his first wife, then held sway, but the gates were shut against him. He then took refuge in Tyre, but was put to death by the governor (B.C. 125). Zubinas recompensed the Tyrians for this act by permitting them to live according to their own laws, and from this period commences what is called by chronologists the era of the independence of Tyre, which was still subsisting at the time of the Council of Chalcedon, 574 years after this event (Joseph. Ant. Iud. xiii. 9, 12, 17; Just. xxxvi. 1, Just. xxxix. 1).
Demetrius II (Greek: Δημήτριος Β` d. 125 BCE), called Nicator (Greek: "Νικάτωρ", i.e. "Victor"), was one of the sons of Demetrius I Soter, brother of Antiochus VII Sidetes and his mother could have been Laodice V. He ruled the Seleucid Empire for two periods, separated by a number of years of captivity in Parthia.