Conversion of Vladimir the Great
The Conversion of Vladimir is a narrative recorded in several different versions in medieval sources about how Vladimir the Great converted from Slavic paganism to Byzantine Christianity in the 980s. In traditional historiography, it is known as the Baptism of Volodimer, and regarded as the highlight of the Christianization of Kievan Rus' (dubbed the Baptism of Rus').
Source: Wikipedia — Conversion of Vladimir the Great (CC BY-SA 4.0)