Constantine IV, surnamed Pogonatus (the Bearded), emperor of the East, born in 648, died in 685. He was the son of Constans II., who in 654 crowned him Augustus, and whom he succeeded in 668. In the following year he conducted a successful expedition into Sicily, but he was hard pressed both by the Saracens and the Bulgarians. To his two brothers he gave the title of Augustus, but allowed them no share in the government. Some of their adherents demanded that they should share the actual sovereignty, urging that as there were three equal persons in the Godhead, so there should be three equal sovereigns on earth. Constantine hung some of the theologians who advanced this argument, and the others agreed to acknowledge his supremacy. The brothers were pardoned; but their claims being again renewed, he caused their noses to be cut off in the presence of the bishops assembled in the sixth general synod of Constantinople. He gained the favor of the church by remitting the payment made on the election of a new pope; and offered the hair of his two sons on the shrine of St. Peter as a symbol of their adoption by the pope.

He was succeeded by his son Justinian II.