The diocesan system of Christian church government in Ireland was set up by the
Synod of Rathbreasail in 1111 and modified by the
Synod of Kells in 1152, replacing the earlier
Celtic Christian monastic model. The island of Ireland is divided into four
ecclesiastical provinces each headed by a metropolitan
archbishop. The provinces were almost co-extensive with their contemporary
civil counterparts. After the
Reformation in Ireland, both the Protestant
Church of Ireland and the Roman Catholic Church saw themselves as successors to the pre-Reformation church. Most bishops were non-resident during the enforcement of the
Penal Laws, but the dioceses continued to exist. Whereas
English Catholic dioceses were forbidden by law from having the same name as a diocese of the established
Church of England, no such prohibition was made for Irish dioceses. The Roman Catholic dioceses remained close to the original, with a few notable differences. Firstly, several dioceses with small populations were merged, and now have more than one name to represent their merger. Secondly, the Diocese of Galway was created in 1831 following the abolition of the
Wardenship of Galway. James Butler 2nd, the Archbishop of Cashel and Emly (1774–91), on being appointed by Rome moved his residence and
cathedra from Cashel, favouring
Thurles instead, where his successors continue to reign today. Similarly, in the
Diocese of Elphin, the
Cathedral, which was originally established in the County Roscommon town of
Elphin, is now in
Sligo. Another change is that the ancient see of Kilfenora has been administered by the Bishop of Galway in the province of Tuam since the late 19th Century. The correct title of the Bishop is now the Bishop of Galway and Kilmacduagh and
Apostolic Administrator of Kilfenora. More recently, the Diocese of Ross merged with the Diocese of Cork to form the
Diocese of Cork and Ross in the 1950s. == Geographic boundaries ==