Catholicism in Ireland

The Catholic Church in Ireland is part of the worldwide Catholic Church, under the spiritual leadership of the pope in Rome. With 4.7 million members, it is the most populous Christian denomination in Ireland, comprising 71.9 percent of the population. The primatial seat is the Archdiocese of Armagh and the Church ministers to Catholics on an all-island basis. The Irish Catholic Bishops' Conference is a consultative body for ordinaries in Ireland.

In 2011, 84.2% of the citizens of the Republic of Ireland and 43.8% of the workforce of Northern Ireland self-identified as Catholic. In the island of Ireland, 4,599,368 people identified themselves as Catholics; 3,861,335 (84.16%) in the Republic of Ireland and 738,033 (40.76%) in Northern Ireland. The combined Catholic populations is 4,599,368, or 71.88% of the overall population.

Ireland was evangelised early in the 5th century by missionaries such as Palladius and Saint Patrick. Until the Norman invasion of Ireland in 1169, the Irish Church practised what is now referred to as Celtic Christianity.

A reform to the Roman style diocesan system developed slowly after the Synod of Rathbreasail in 1111. In 1155, Pope Adrian IV, the English born Pope, issued a papal bull known as Laudabiliter. This gave King Henry II of England permission to invade Ireland as a means of strengthening the Papacy's control over the Irish Church. The Norman invasion of Ireland began in 1169, under the authority of this bull. Adrian IV's successor, Pope Alexander III, ratified the Laudabiliter and gave Henry dominion over the "barbarous nation" of Ireland so that its "filthy practises" may be abolished, its Church brought into line, and that the Irish pay their tax to Rome. After the Norman invasion, a greater number of foreign-born prelates were appointed.

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