Religion in the Republic of Ireland
The predominant religion in the Republic of Ireland is Christianity, with the largest church being the Roman Catholic Church. The Irish constitution says that the state may not endorse any particular religion and guarantees freedom of religion.
Catholic Church in Ireland
The Government of Ireland Act of 1920 acted as the constitution of Northern Ireland, in which was enshrined freedom of religion for all of Northern Ireland's citizens. Here Catholics formed a minority of some 35 percent of the population, which had mostly supported Irish nationalism and was therefore historically opposed to the creation of Northern Ireland.