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.
Religion in Northern Ireland
Secularisation in Northern Ireland has followed different paths within each of the two main communities, being at a more advanced stage within the mainly Protestant community in which it is reflected more often with a formal move away from the churches and by expressing no formal religious attachment, mirroring the pattern in Great Britain, whereas in the mainly Catholic community it is reflected by declining mass attendance but often with retaining a formal Catholic identification, mirroring the pattern in the Republic of Ireland. Those stating that they had no religion in the 2011 census were concentrated in largely Protestant areas, suggesting that they were mostly from a Protestant background.