Baptism of Kiev

The Christianization of Kievan Rus' took place in several stages. In early 867, 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. Following the Primary Chronicle, the definitive Christianization of Kievan Rus' dates from the year 988 (the year is disputed), when Vladimir the Great was baptized in Chersonesus and proceeded to baptize his family and people in Kiev. The latter events are traditionally referred to as baptism of Rus' (Russian: Крещение Руси, Ukrainian: Хрещення Русі) in Russian and Ukrainian literature.

According to the Church Tradition, Christianity was first brought to the territory of modern Belarus, Russia and Ukraine by Saint Andrew, the first Apostle of Jesus Christ. He traveled over the Black Sea to the Greek colony of Chersonesus Taurica in Crimea, where he converted several thousand men to new faith. Allegedly Saint Andrew traveled also north along the Dnieper River, where Kiev would be founded around the 5th century, and as far north as the future location of Veliky Novgorod. The legendary account of the Russian Primary Chronicle tells that Saint Andrew was amused by the Slavic customs of washing in hot steam bath, banya, on his way.

...
Wikipedia