Constantine IX Monomachos

Constantine IX Monomachos (Medieval Greek: Κωνσταντῖνος Μονομάχος, romanized: Kōnstantinos IX Monomachos; c. 980/c. 1000 – 11 January 1055) reigned as Byzantine emperor from June 1042 to January 1055. Empress Zoë Porphyrogenita chose him as a husband and co-emperor in 1042, although he had been exiled for conspiring against her previous husband, Emperor Michael IV the Paphlagonian. The couple shared the throne with Zoë's sister Theodora Porphyrogenita. Zoë died in 1050, and Constantine continued his collaboration with Theodora until his own death five years later.

Constantine waged wars against groups which included the Kievan Rus', the Pechenegs and, in the East, the rising Seljuq Turks. Despite the varying success of these campaigns, the Byzantine Empire largely retained the borders established after the conquests of Basil II (r. 976–1025), even expanding eastwards when Constantine annexed the wealthy Armenian kingdom of Ani. Constantine accordingly may be considered the last effective emperor during the Macedonian Renaissance.

In 1054, a year before Constantine's death, the Great Schism between the Eastern Orthodox and Roman Catholic Churches took place, culminating in Pope Leo IX excommunicating the Patriarch Michael Keroularios. Constantine, aware of the political and religious consequences of such a disunion, made unsuccessful efforts to prevent the breach.