The early history of Christianity in Wales is obscure; continuity from late Roman times has been suggested. In the 6th cent. there were several outstanding Welsh saints (e.g. David, Deiniol, and Dubricius); according to their Lives, they founded large monasteries. Some of these were also the seat of a bishop, and three of them (St Asaph, St Davids, and Bangor), together with the later foundation of Llandaff, eventually emerged as territorial bishoprics. The Welsh Church remained conservative, but eventually adopted the Roman date for Easter from 768. After the Norman conquest the Welsh sees were gradually subjected to the supremacy of Canterbury, and in the 12th cent. diocesan and parochial boundaries began to be defined. The system of tithes was instituted, and by the end of the 13th cent. a judicial and administrative organization was in being. Latin monasticism also was introduced by the Norman invaders. In the later Middle Ages, however, the Welsh Church suffered to a special degree from inertia, and the religious houses were seriously undermanned. The breach with Rome and the dissolution of the monasteries aroused little opposition; the greatest upheaval was caused by Mary Tudor's brief attempt to impose clerical celibacy. Elizabeth I appointed resident, active, Welsh-speaking bishops, who imposed the 1559 settlement, and a Welsh Bible and Prayer Book were authorized by an Act of 1563.
The beginnings of Nonconformity in Wales are represented by the foundation of a ‘gathered’ Church at Llanfaches in 1639. The influence of the established Church declined; the Welsh sees were poor and often held by absentees hopeful of translation, and lay impropriation of tithes ensured that most parish clergy were poor and ill-educated. Methodism, preached by H. Harris, spread rapidly, though its adherents remained within the Church until the Calvinistic Methodists broke away in 1811. The Church failed to adapt to the large increase in population, Nonconformity grew, and religious differences echoed social and political divisions. The disestablishment of the Church of Ireland (1869) and the Englishness of the Church in Wales led to demands for disestablishment. An Act of 1914 eventually disestablished the Welsh Church; it took effect in 1920. A separate province was created; the bishops are nominated by electors representing various elements in the Church, and one of the diocesans is elected Archbishop of Wales. The Church in Wales is no longer Eglwys Loegr (the ‘English Church’); services are conducted in Welsh as well as in English, and after 1920 it increased in numbers and influence. Welsh Nonconformity lost a unifying objective and Welsh nationalism turned to secular objectives. The Calvinist Methodists are still the most numerous of the Free Churches; the Baptists and Independents remain strong, but in the United Reformed Church and among the Wesleyans there has been a marked decline in numbers. The RCs are a small but vigorous community, recruited largely from Irish immigrant stock in the SE; there is a RC Abp. of Cardiff and Bps. of Menevia (whose cathedral is in Swansea) and Wrexham. There is a Greek Orthodox community in Cardiff.