The Catholic Church in Ireland or Irish Catholic Church, is part of the worldwide Catholic Church in communion with the Holy See. With 3.7 million members, it is the largest Christian church in Ireland. In the Republic of Ireland's 2016 census, 78% of the population identified as Catholic; this was 6% lower than the 2011 figure. By contrast, 41% of people in Northern Ireland identified as Catholic at the 2011 census; it is expected that this proportion will increase in the coming years. The Archbishop of Armagh, as the Primate of All Ireland, has ceremonial precedence in the church. The church is administered on an all-Ireland basis. The Irish Catholic Bishops' Conference is a consultative body for ordinaries in Ireland.

Armagh is the county town of County Armagh and a city in Northern Ireland, as well as a civil parish. It is the ecclesiastical capital of Ireland – the seat of the Archbishops of Armagh, the Primates of All Ireland for both the Roman Catholic Church and the Church of Ireland. In ancient times, nearby Navan Fort was a pagan ceremonial site and one of the great royal capitals of Gaelic Ireland. Today, Armagh is home to two cathedrals and the Armagh Observatory, and is known for its Georgian architecture.