The Christianization of Poland refers to the introduction and subsequent spread of Christianity in Poland. The impetus to the process was the Baptism of Poland, the personal baptism of Mieszko I, the first ruler of the future Polish state, and much of his court. The ceremony took place on the Holy Saturday of 14 April 966, although the exact location is still disputed by historians, with the cities of Poznań and Gniezno being the most likely sites. Mieszko's wife, Dobrawa of Bohemia, is often credited as a major influence on Mieszko's decision to accept Christianity.

While the spread of Christianity in Poland took centuries to finish, the process was ultimately successful, as within several decades Poland joined the rank of established European states recognised by the papacy and the Holy Roman Empire. According to historians, the baptism of Poland marks the beginning of Polish statehood. Nevertheless, the Christianization was a long and arduous process, as most of the Polish population remained pagan until the pagan reaction during the 1030s.