Anastasius, the name of two emperors of Constantinople. I. Surnamed Dicorus, born about 430, died in 518. He was a member of the lifeguard (silentiarii) of the emperor Zeno, on whose death in 491 he was proclaimed emperor through an intrigue with the empress Ariadne, whom he soon afterward married. Though more than 60 years of age, he began his stormy reign by suppressing with great ability a rebellion organized against him by Longinus, Zeno's brother, who had aspired to the throne, and by two other natives of the Isaurian province, whose names were also Longinus. Rebellions, plagues, earthquakes, and a severe famine tilled the next years of his reign with hardship for the people and difficulty for the emperor; and finally the Persians under their king Cabades invaded the empire with such success, that Anastasius was compelled to purchase peace by an enormous tribute (505). In the opening years of the 6th century Anastasius became involved in the religious disputes of the time, and was anathematized by Pope Symmachus for favoring the Eutychian heresy.

II. Originally named Artemius, chosen emperor in 713 as successor to Philippicus, whose minister he had been. He began his reign by punishing Rufus, the traitor who had deposed Philippicus. In 715 he undertook an expedition against the Arabs, but it was rendered futile by the mutiny of many of the sailors of his fleet. The mutineers proclaimed as emperor one Theodosius, a government official, who besieged Constantinople and Nicaea, in which latter place Anastasius was when attacked. The latter was driven from the throne (716), and retired to a monastery, while the rebel became emperor as Theodosius III. In the reign of Leo III. Anastasius endeavored to regain the throne, but was defeated and put to death (721).