emperor of the East A. D. 578-582. His full name was ANICIUS THRAX, FLAVIUS CONSTANTINUS. He was captain of the guards to the emperor Justinus II., who elevated him to the rank of Caesar or Augustus, A. D. 574. He was a native of Thrace, whence he has the addition of Thrax to his name. He assumed the name of Constantinus after he became emperor. The date of his birth is uncertain. He was brought up at the court of Justinian, and employed by Justinus II., who succeeded Justinian A. D. 565. In A. D. 573 Tiberius commanded the imperial troops against the Avars, in the neighbourhood of the Save and the Danube. He lost one battle against them, but he soon recovered this failure, and secured for the empire the possession of Sirmium, near the junction of the Save and the Danube. Justinus, feeling himself incompetent for the labour of administration, associated Tiberius with him, and it is said that the influence of his wife Sophia, who admired the handsome captain, contributed to determine the emperor's choice. The speech which the emperor addressed to Tiberius on this occasion is preserved by Theophylactus Simocatta, and has been translated by Gibbon : it contained wise advice, and Tiberius followed it. Justinus survived this ceremony four years, during which the weight of administration fell on Tiberius alone.

The Longobards were now in Italy, but a war with Persia prevented Tiberius from directing all his attention to that quarter. Yet he maintained his authority in the exarchate of Ravenna, and in other parts of Italy, and he saved Pelagius II., the pope of Rome, and the Roman citizens, from the Longobards, by a timely supply of provisions, which were forwarded by a fleet. To check the progress of the Longobards in the north of Italy, he concluded an alliance some years later with Chilperic the king of the Franks. The war with Chosroes, king of Persia, demanded all the resources of Tiberius. In A. D. 576. Justinian, who was in command of the armies of the Eastern Empire, crossed the Bosporus with a force of 150,000 men, to relieve Theodosiopolis in Armenia, which was defended by Theodorus, a Byzantine general. This force comprehended a great number of Germans and Slavonians. A battle was fought with Chosroes near Melitene in Armenia, in which the Persians were defeated, and many of them perished in the Euphrates. An immense booty, carried by twenty-four elephants, was brought to Constantinople. Justinian is said to have advanced into the very centre of the Persian empire, and was about concluding a treaty with Chosroes, but it was interrupted by some advantage gained over Justinian by one of the generals of Chosroes. Justinian was recalled. and Mauricius, afterwards the successor of Tiberius was appointed to command in his place. Mauricius secured himself against sudden attacks by adopting the old Roman plan of never resting, except in an entrenched camp. The winter (A. D. 577-578) Mauricius spent in Mesopotamia.

Justinus died on the fifth of October A. D. 578, and Tiberius was now sole emperor. Sophia, it is said, hoped to become the wife of Tiberius, but when the people in the Hippodrome called for the new empress, Tiberius produced as his wife Anastasia, to whom he had been for some time secretly married. Sophia, though treated with respect by the new emperor, and enjoying an ample allowance, could not forget her disappointment, and she is said to have induced Justinian to conspire with her to overthrow the man whom she had loved. The plot was discovered : Sophia was deprived of all power of doing further mischief, and Justinian, who was pardoned, became a faithful friend of Tiberius.

In A. D. 579 Chosroes, the Persian, was succeeded by Hormisdas, and the war began again. Mauricius defeated the Persians, overran a large part of Persia, and in a bloody contest on the Euphrates, A. D. 580, gave the forces of Hormisdas a most signal defeat; and again in the following year. In Africa, which had long been disturbed by the natives, Gennadius, the exarch of Ravenna, defeated (A. D. 580) Gasmul, king of the Mauritani. Mauricius enjoyed a triumph at Constantinople for his Persian victories, A. D. 581, and in August of that year, Tiberius, whose health was rapidly failing, raised him to the dignity of Caesar, having no sons of his own. He also gave him his daughter Constantina in marriage. Tiberius died on the 14th of August, A. D. 582, and was succeeded by Mauricius.

Tiberius was universally regretted. By an economical administration he diminished the taxation of his subjects, and always had his treasury full.

There were at least six constitutions of the emperor Tiberius; three of which (Nos. 161, 163, 164) form part of the collection of 168 Novellac, one is found by itself in the Venice manuscript, the fifth is lost, and the sixth only exists in Latin. The constitution (No. 163, Περὶ κουφισμῶν δημοσίων, "On the Diminution of Taxes," expresses a humane desire to relieve the people from their burdens, combined with a prudent regard to supply the necessary demands of the state. (Gibbon, Decline and Fall, &c., ch. 45, who also gives the references to the authorities for the reign of Tiberius; Mortreuil, Hist. du Droit Byzantin, vol. i.p. 81.)