The Archbishopric of Moravia (Latin: Sancta Ecclesia Marabensis) was an ecclesiastical province, established by the Holy See to promote Christian missions among the Slavic peoples. Its first archbishop, the Byzantine Methodius, persuaded Pope John VIII to sanction the use of Old Church Slavonic in liturgy. Methodius had been consecrated archbishop of Pannonia by Pope Adrian II at the request of Koceľ, the Slavic ruler of Pannonia in East Francia in 870.
Methodius's appointment was sharply opposed by the Bavarian prelates, especially the Archbishop of Salzburg and the Bishop of Passau, because missionaries from their dioceses had already been active for decades in the territory designated to Methodius, including Pannonia and Moravia. Methodius was soon captured and imprisoned. He was only released in 873 on Pope John VIII's order. He settled in Moravia which emerged as a leading power in Central Europe during the next decade in the reign of Svatopluk. However, most clerics, who had come from East Francia, were hostile to the archbishop, who introduced Byzantine customs and promoted the use of vernacular in liturgy. They accused Methodius of heresy, but he convinced the pope of the orthodoxy of his views. The pope also strengthened Methodious's position, declaring that all clerics in Moravia, including the newly consecrated bishop of Nitra, were to be obedient to Methodius in 880.
Methodius died on 6 April 885. Wiching, Bishop of Nitra, who had always been hostile to the archbishop, expelled his disciples from Moravia. No new archbishop was appointed, and Wiching, who remained the only prelate with a see in Moravia, settled in East Francia in the early 890s. Church hierarchy was only restored in Moravia when the legates of Pope John IX consecrated an archbishop and three bishops around 899. However, the Magyars occupied Moravia in the first decade of the 10th century.