II. (Φαρνάκης), king of Pontus, or more properly of the Bosporus, was the son of Mithridates the Great. According to Appian he was treated by his father with great distinction, and even designated as his successor, but we find no mention of him until the close of the life of Mithridates, after the latter had taken refuge from the arms of Pompey in the provinces north of the Euxine. But the schemes and preparations of the aged monarch for renewing the war with the Romasns, and even carrying his arms into the heart of their empire, excited the alarm of Pharnaces, and he took advantage of the spirit of discontent which existed among the assembled troops to conspire against the life of his father. His designs were discovered; but he was supported by the favour of the army, who broke out into open mutiny, declared Pharnaces their king, and marched against the unhappy Mithridates, who, after several fruitless appeals to his son, was compelled to put an end to his own life, B. C. 63. (Appian. Mithr. 110, 111; D. C. 37.12. For further details and authorities see MITHRIDATES.) In order to secure himself in the possession of the throne which he had thus gained by parricide, Pharnaces hastened to send an embassy to Pompey in Syria, with offers of submission, and hostages for his fidelity, at the same time that he sent the body of Mithridates to Sinope to be at the disposal of the Roman general. Pompey readily accepted his overtures, and granted him the kingdom of the Bosporus with the titles of friend and ally of the Roman people. (Appial. Mithr. 113, 114; Dio Cass. xxxvii 14.)

For some time Pharnaces appears to have remained contented with the limits thus assigned him; and we know no events of his reign during this period, except that he entered into extensive relations, both hostile and friendly, with the surrounding Scythian tribes. (Strab. xi. p.495, 506.) But the increasing dissensions among the Romans themselves emboldened him to turn his arms against the free city of Phanagoria, which had been expressly excepted from the grant of Pompey, but which he now reduced under his subjection. Not long afterwards, the civil war having actually broken out between Caesar and Pompey, he deterninsd to seize the opportunity to reinstate himself in his father's dominions, and made himself master, almost without opposition, of the whole of Colchis and the lesser Armenia. Hereupon Deiotarus, the king of the latter country, applied to Domitius Calvinus, the lieutenant of Caesar in Asia, for his support, which was readily granted; but the combined forces of the Roman general and the Galatian king were totally defeated by Pharnaces near Nicopolis in Armenia, and the latter was now enabled to occupy the whole of Pontus, including the important cities of Amisus and Sinope. (Appian. Mithri. 120; D. C. 13.45, 46; Hirt. B. Alex. 34-41; Strab. xii. p.547.) He now received intelligence of the revolt of Asander, to whom he had entrusted the government of Bosporus during his absence, and was preparing to return to chastise his rebel officer, when the approach of Caesar himself corn. pelled him to turn all his attention towards a more formidable enemy. Pharnaces at first endeavoured to conciliate the conqueror by peaceful messages and offers of submission, with the view of gaining time until the affairs of Rome should compel the dictator to return thither. But the rapidity and decision of Caesar's movements quickly disconcerted these plans, and brought on a decisive action near Zela, in which the army of Pharnaces was utterly defeated, and he himself with difficulty made his escape with a small body of horsemen to Sinope. From thence he proceeded by sea to the Bosporus, where he assembled a force of Scythian and Sarmatian troops, with which he regained possession of the cities of Theodosia and Panticapaeum, but was ultimately defeated and slain by Asander. According to Appian, he died in the field fighting bravely; Dio Cassius, on the contrary, states that he was taken prisoner, and subsequently put to death. (Appian, App. Mith. 120; D. C. 42.45-48; Hirt. Bell. Alex. 65-77; Plut. Caes. 50; Suet. Jul. 35.)

Pharnaces was about fifty years old at the time of his death (Appian, l.c.), of which he had reigned nearly sixteen. It appears that he left several sons, one of whom, named Dareius, was for a short time established by Antony on the throne of Pontus. (Appian, App. BC 5.75; Strab. xii. p.560.) His daughter Dynamis was married to Polemon I. king of Bosporus. (D. C. 54.24.)