Romanus IV (Romanus Diogenes), d. 1072, Byzantine emperor (1068-71). A Cappadocian general, he succeeded Constantine X by marrying his widow, Eudocia Macrembolitissa. After some early successes against the Seljuk Turks he was crushingly defeated and captured (1071) by Alp Arslan at Manzikert. He was ransomed and promised to pay tribute, but he was deposed and blinded by his stepson, Michael VII, and soon died.