<P> By the mid-10th century , there was already a Christian community among Kievan nobility , under the leadership of Greek and Byzantine priests , although paganism remained the dominant religion . Princess Olga of Kiev was the first ruler of Kievan Rus to convert to Christianity , either in 945 or 957 . Undoubtedly influenced by his Christian grandmother and by a proposed marriage alliance with the Byzantine imperial family , Olga 's grandson Vladimir I ( c. 956 - 1015 ) prince of Kiev , from among several options , chose the Byzantine rite . Baptized in 988 , he led the Kievans to Christianity . This date is often considered the official birthday of the Russian Orthodox Church . Thus , in 1988 , the Church celebrated its millennial anniversary . </P>
who helped the rise of orthodox christianity in russia by converting to the religion
Princess Olga of Kiev Vladimir I ( c. 956 - 1015 ) prince of Kiev