 Ireland 's largest religious group is Christianity . The largest denomination is Roman Catholicism representing over 73 % for the island ( and about 87 % of the Republic of Ireland ) . Most of the rest of the population <unk> to one of the various Protestant denominations ( about 48 % of Northern Ireland ) . The largest is the Anglican Church of Ireland . The Muslim community is growing in Ireland , mostly through increased immigration , with a 50 % increase in the republic between the 2006 and 2011 census . The island has a small Jewish community . About 4 % of the Republic 's population and about 14 % of the Northern Ireland population describe themselves as of no religion . In a 2010 survey conducted on behalf of the Irish Times , 32 % of <unk> said they went to a religious service more than once a week . 
