Christianity in Ireland

Christianity (Irish: Críostaíocht) is, and has been the largest religion in Ireland since the 5th century. After a pagan past of Antiquity, missionaries, most famously including Saint Patrick, converted the Irish tribes to Christianity in quick order, producing a great number of saints in the Early Middle Ages, and a faith interwoven with Irish identity for centuries since − though less so in recent times.

Most Christian churches are organized on an "all-Ireland" basis, including both the Republic of Ireland and Northern Ireland. In the Republic of Ireland, 69% of the population adheres to the Catholic Church. In Northern Ireland, the various branches of Protestantism collectively form a plurality of the population, but the single largest church is the Catholic Church, which accounts for some 40.8% of the population. There is also a small presence of other churches, such as the Eastern Orthodox Church growing at the beginning of the 21st century.

Despite being a nation once noted for perpetually intense Christian faith and mores even a couple generations ago in the early 20th century, a "Quiet Revolution" like the Quiet Revolution of Quebec has taken place and Ireland has become increasingly secular in most aspects of society. The 1972 amendment of the Irish constitution, for example, removed the "special position" of the Catholic Church as "guardian of the Faith" and the recognition of other named religious denominations in Ireland. But, in 1983 abortion was banned by the Eighth Amendment of the Irish constitution which recognized the right to life of the unborn as equal to the right to life of the mother and was advocated for by representatives of the Catholic Church. Only in 2018 was a referendum held to repeal the Eighth Amendment, and this repeal marks a significant point in the secularization of the constitution made possible by a significant secularization of the people. Today, a large proportion of Irish Christians are nominally so, and adhere to the identity despite a secular lifestyle for reasons ranging from cultural to apathetic. Catholicism is now in serious decline in the Republic of Ireland.