Sergius II of Constantinople was an Eastern Orthodox prelate who served as the Ecumenical Patriarch from 1001 until his death in July 1019. Before his elevation to the patriarchal see, he acted as the abbot of the Monastery of Manuel, a monastery originally established by Photius I. Historical accounts by John Skylitzes suggest that he was a relative of the famous 9th-century patriarch Photius I. He held his position during the Byzantine Empire and was succeeded by Eustathius.