The Christianization of Poland began in the 10th century when Mieszko I, the first historical ruler of Poland, converted to Christianity. This event is often marked by his baptism in 966, which helped to establish ties with the Holy Roman Empire and the Roman Catholic Church. Mieszko's conversion encouraged the spread of Christianity among his subjects, leading to the establishment of churches and the integration of Christian practices into Polish society. By the end of the 11th century, Christianity had become the dominant religion in Poland. The process involved the gradual conversion of the nobility and the common people, supported by missionaries and the church. This transformation played a crucial role in shaping Polish culture, identity, and political structure, ultimately leading to the formation of a unified Polish state under Christian principles.