The Primacy of Ireland was historically disputed between the Archbishop of Armagh and the Archbishop of Dublin until finally settled by Pope Innocent VI. Primate is a title of honour denoting ceremonial precedence in the Church, and in the Middle Ages there was an intense rivalry between the two archbishoprics as to seniority. Since 1353 the Archbishop of Armagh has been titled Primate of All Ireland and the Archbishop of Dublin Primate of Ireland, signifying that they are the senior churchmen in the island of Ireland, the Primate of All Ireland being the more senior. The titles are used by both the Roman Catholic and Church of Ireland bishops. The distinction mirrors that in the Church of England between the Primate of All England, the Archbishop of Canterbury, and the Primate of England, the Archbishop of York.
The episcopal see of Dublin was created in the eleventh century, when Dublin was a Norse city state. Its first bishop, Dúnán (or Donatus), was described at his death as "chief bishop of the Foreigners". From the first, Dublin had close ties to the see of Canterbury. The fifth bishop of Dublin, Gregory, was only a subdeacon when he was elected bishop by what Aubrey Gwynn called "the Norse party in the city". He was sent to England where he was consecrated by Archbishop Ralph of Canterbury, but on his return he was prevented from entering his see by those who wanted Dublin integrated with the Irish hierarchy. A compromise was reached by which Gregory was recognised as bishop of Dublin, while he in turn accepted the authority of Cellach, archbishop of Armagh, as primate. In 1152, the Synod of Kells divided Ireland between the four archdioceses of Armagh, Dublin, Cashel and Tuam. Gregory was appointed archbishop of Dublin. The papal legate, Cardinal John Paparo, also appointed the archbishop of Armagh "as Primate over the other bishops, as was fitting."