Christianization of Kievan Rus'

The Christianization of Kievan Rus' took place in several stages. In early 988, Patriarch Photius of Constantinople announced to other Orthodox patriarchs that the Rus', baptised by his bishop, took to Christianity with particular enthusiasm. Photius's attempts at Christianizing the country seem to have entailed no lasting consequences, since the Primary Chronicle and other Slavonic sources describe the tenth-century Rus' as firmly entrenched in paganism. The definitive Christianisation of Kiev dates from the late 980s (the year is disputed), when Vladimir the Great was baptized at Chersonesos, proceeding to baptize his family and people in Kiev. The place of Vladimir's baptism is marked by St. Vladimir's Cathedral.

Read more about Christianization Of Kievan Rus':  Prehistory, Ninth Century, Tenth Century, Aftermath