Igor (ēˈgôr, Russ. ēˈgər) [key] or Ihor ēˈkhər, d. 945, duke of Kiev (912–45), successor of Oleg as ruler of Kievan Rus. According to the Russian Primary Chronicle, a medieval history, Igor was the son of Rurik, founder of the Russian princely line. Igor's expedition (941) against Constantinople was routed by the Greeks, and in 945 he concluded a new commercial treaty with the Byzantines. He was killed by rebellious Slavic tribespeople while attempting to collect tribute. His wife, St. Olga or Olha, served as regent for their son Sviatoslav after Igor's death.