Oleg (ō´leg, Rus. ôlĕk´) or Oleh (ôlĕkh´), d. c.912, founder of Kievan Rus. Succeeding his kinsman Rurik as leader of the Varangians at Novgorod, Oleg led forth his retainers to seize Kiev (c.879). He made Kiev his capital and set about uniting the Slavic tribes along the Volkhov-Dnieper waterway, freeing them from the overlordship of the Khazars. Oleg concluded commercial treaties with the Byzantine Empire in 907 and 911, making trade with the empire a major factor in the Kievan economy and opening the path for Greek Christian cultural penetration. Oleg was succeeded by Igor.