Constantine X (circa 1006-1067), surnamed Ducas, was Roman emperor of the East from 1059 to 1067. He was a typical representative of the civilian aristocracy. By deliberate neglect of the armed forces he reduced the Byzantine Empire to impotence when it was in mortal danger from Normans, Magyars, Uzes, and, most of all, Seljuk Turks.
His policy made the disaster of Manzikert (1071), where the Seljuks overwhelmingly defeated the Roman army, inevitable. He died in May 1067.