The history of Christianity in the Czech Lands began in the 9th century. Moravia was the first among the three historical regions of what now forms the Czech Republic whose ruling classes have officially adopted Christianity, between 830s and 860s. In 845 Bohemian chieftains or duces also converted to the new faith, but it was just short-lived political gesture (next year they returned to paganism); real beginning of efforts to promote Christianity in Bohemian territory have to be put to the period after 885. Moravia was the earliest center of Old Church Slavonic liturgy after the arrival of Constantine (Cyril) and Methodius in 863, but their opponents, mainly priests of German origin, achieved the banishment of their disciplines in the 880s. Bohemia became the center of Christianization following the fall of Moravia in the early 10th century. Changes in burials and the erection of churches throughout the Czech Lands demonstrate the spread of the new faith in the 10th century.
Two dioceses (the bishoprics of Prague and Olomouc) came into being by the end of the 11th century, but the system of local parishes only strengthened in the 12th century. The dukes and wealthy noblemen also set up a number of Benedictine, Cistercian, and Premonstratensian monasteries in the 11th and 12th centuries.
Early Middle Ages (till 976)
Early Slavs (before c. 830)
Archaeological finds with close analogies in Ukrainesunken huts with corner ovens, small cremation cemeteries, and "Prague pottery"suggests that the first Slavic-speaking groups settled in the lands now inhabited by the Czech people in the second half of the 6th century. Almost all information on early Slavic mythology and cults derives from sources first recorded in the late 10th century. According to these sources, the Czechs' ancestors worshipped Perun, Veles, and other deities of the Slavic pantheon.
The remains of pagan cult sites, most of which have been excavated in Moravia, are "difficult to interpret." For instance, finds at a cemetery at Mikulčice which was in use from the late 8th century to the middle of the 10th century point at the existence of a rite connected to horse burials. The earliest inhumation graves, dated to the 8th century, were also unearthed in this region. Fortifications at Mikulčice, Staré Město, and nearby settlements proves that important centers of power existed in the valley of the river Morava.
Likewise around 800, strongholds were erected at Kouřim and other places in the Vltava river's valley in Bohemia. Charlemagne's biographer Einhard lists the "Bohemians" among the peoples with whom Charlemagne "had armed conflict." The heads or duces of the Bohemian tribes agreed to pay tribute to the emperor in 805 and 806. Bohemian and Moravian emissaries participated at the Diet of Frankfurt in the Carolingian Empire in 822.
Beginnings (c. 830–c. 906)
The earliest Christian missionaries came to Moravia from the dioceses of Passau, Regensburg, and Salzburg. The Frankish aristocrats' way of life attracted the Moravian and Bohemian leaders who identified it with Christianity. The adoption of the new faith was initially the personal decision of individual aristocrats. Czech religious terminology also indicates the chieftains' preeminent role in Christianization. For instance, the Czech word for church (kostel) derived from Old High German kastel ("fortress") and the word for priest (kněz) from Common Slavonic kŭnędzĭ ("prince or chieftain"). Reginhar, bishop of Passau, baptized "all Moravians" and their prince, Mojmir I (r. c. 830–846) in 831, at least according to the Reports of the Bishops of Passau. Crosses from graves at fortresses suggest that most Moravian chieftains converted to Christianity by the 850s, but the Frankish prelates described the Church in Moravia as "coarse" at their synod of 852. Indeed, the pagan temple at Mikulčice which was in use till around 850 demonstrates that heathen cults survived the official adoption of the new faith.
No objects connected to Christianity which can be dated to the period before the mid-9th century have been unearthed in Bohemia. The Annals of Fulda writes of "fourteen of the duces of the Bohemians" who visited Louis the German in Regensburg where they were baptised "on the octave of the Epiphany," that is on January 13, 845. The Czech chieftains hoped that their conversion could contribute to maintain the peace with the Franks, because they soon returned to paganism after Louis the German invaded the Christian Moravia and dethroned Mojmir I in 846.