The Christianization of Kievan Rus began in the late 10th century, primarily under the rule of Prince Vladimir the Great. In 988, Vladimir adopted Eastern Orthodox Christianity as the state religion, leading to the baptism of the population in the Dnieper River. This significant event marked the transition from pagan beliefs to Christianity, influencing the culture and governance of the region. The adoption of Christianity helped unify the diverse tribes of Kievan Rus and established stronger ties with the Byzantine Empire. It also encouraged the development of literacy, art, and architecture, as religious institutions became centers of learning and culture in the region.