The Roman Catholic Archdiocese of Armagh (Latin: "Archidioecesis Ardmachana"; Irish: "Ard-Deoise Ard Mhacha") is a Latin ecclesiastical jurisdiction of the Catholic Church situated in Northern Ireland. Its ordinary is the Archbishop of Armagh, who serves concurrently as the metropolitan of the ecclesiastical province of Armagh and holds the title of Primate of All Ireland, the highest-ranking prelate in the Irish Catholic hierarchy.
The mother church of the archdiocese is St Patrick's Cathedral, a site of profound historical and spiritual significance. The archdiocese’s claim to primatial status is rooted in its founding by Saint Patrick circa 445, establishing it as the principal see of Irish Christianity. Its recognition as a metropolitan province was formalized in 1152 by the Synod of Kells, affirming its ecclesial preeminence.