There is evidence that the first Christian bishop was sent to Novgorod from Constantinople either by Patriarch Photius or Patriarch Ignatios, c. By the mid-10th century, there was already a Christian community among Kievan nobility, under the leadership of Byzantine Greek 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.
The ROC, as well as the primate thereof, officially ranks fifth in the Orthodox order of precedence, immediately below the four ancient Patriarchates of the Greek Orthodox Church, those of Constantinople, Alexandria, Antioch, and Jerusalem.
The official Christianization of Kievan Rus' widely seen as the birth of the ROC is believed to have occurred in 988 through the baptism of the Kievan prince Vladimir and his people by the clergy of the Ecumenical Patriarchate whose constituent part the ROC remained for the next six centuries, while the Kievan see remained in the jurisdiction of the Ecumenical Patriarchate until 1686.
The Kievan church was a junior metropolitanate of the Patriarchate of Constantinople and the Ecumenical patriarch appointed the metropolitan, who usually was a Greek, who governed the Church of Rus'.