The Church of Ireland (Irish: Eaglais na hÉireann; Ulster-Scots: Kirk o Airlann) is a Christian church in Ireland and an autonomous province of the Anglican Communion. It is organised on an all-Ireland basis and is the second-largest Christian church on the island after the Catholic Church. Like other Anglican churches, it has retained elements of pre-Reformation practice, notably its episcopal polity, while rejecting the primacy of the Bishop of Rome. In theological and liturgical matters, it incorporates many principles of the Reformation, particularly those espoused during the English Reformation. The church self-identifies as being both Catholic and Reformed. Within the church, differences exist between those members who are more Catholic-leaning (high church) and those who are more Protestant-leaning (low church or evangelical). For historical and cultural reasons, the Church of Ireland is generally identified as a Protestant church.
The Church of Ireland describes itself as
that part of the Irish Church which was influenced by the Reformation, and has its origins in the early Celtic Church of St Patrick.
The Church of Ireland considers itself Catholic because it is in possession of a continuous tradition of faith and practice, based on scripture and early traditions, enshrined in the Catholic creeds, together with the sacraments and apostolic ministry. However, the Church of Ireland is also Protestant, or Reformed, since it opposes doctrines and ways of worshipping that it considers contrary to scripture and which led to the Reformation.
The Church of Ireland, as a Reformed and Protestant Church, doth hereby re-affirm its constant witness against all those innovations in doctrine and worship whereby the Primitive faith hath been from time to time defaced or overlaid, and which at the Reformation this Church did disown and reject.
When the Church of England broke communion with the Holy See, the church became the established church of Ireland, assuming possession of most church property and so retaining a great repository of religious architecture and other items, though some were later destroyed. The church explains its possession of so many of the ancient church buildings of Ireland by reference to the precedent set by Emperor Constantine the Great in the 4th century: