Additionally, the cathedra of the Roman Catholic Archdiocese of Cashel and Emly was originally in the town prior to the English Reformation.

The Rock of Cashel, to which the town below owes its origin, is an isolated elevation of stratified limestone, rising abruptly from a broad and fertile plain called the Golden Vale.

Originally known as Fairy Hill, or Sid-Druim, the Rock was, in pagan times, the dun, or castle, of the ancient Eoghnacht Chiefs of Munster.

In 977 the Dál gCais usurper, Brian Boru, was crowned here as the first non-Eóghanacht king of Cashel and Munster in over five hundred years.

In 1101 his great-grandson, King Muirchertach Ua Briain, gave the place to the bishop of Limerick, thus denying it forever to the MacCarthys, the senior branch of the Eóganachta.

It has been suggested that the seventh act of the Synod called upon the clergy and people of Ireland to acknowledge Henry II of England as their king.

Over 1,000 Irish Catholic soldiers and civilians, including several prominent clerics, were killed in the attack and ensuing massacre.

The Tripartite Life of the saint relates that while "he was baptising Aengus the spike of the crozier went through the foot of the King" who bore with the painful wound in the belief "that it was a rite of the Faith".

According to the same authority, twenty-seven kings of the race of Aengus and his brother Aillil ruled in Cashel until 897, when Cerm-gecan was slain in battle.

At the synod of Kells, 1152, Cardinal Paparo gave a pallium to Donat O'Lonergan of Cashel, and since then his successors have ruled the ecclesiastical province of Munster.

During the episcopate of Donal O'Hullican (1158–1182), the King of Limerick, Domnall O'Brien, built in 1169 a more spacious church beside Cormac's Chapel, which then became a chapterhouse.

Maurice, a Geraldine, filled the see from 1504 to 1523, and was succeeded by Edmund Butler, prior of Athassal Abbey, who was a natural son of Pierce, Earl of Ormond.

In addition to the wars between the Irish and the English there arose a new element of discord, the Anglican Reformation introduced by Henry VIII Tudor.

While residing at Kilmeaden Castle Archbishop Butler levied black-mail on the traders of the Suir, robbing their boats and holding their persons for ransom.

At a session of the royal privy council held at Clonmel in 1539, he swore to uphold the spiritual supremacy of the king and denied the power in Ireland of the Bishop of Rome.

After a vacancy of six years, Maurice FitzGibbon (1567–1578), a Cistercian abbot, was promoted to the archbishopric by Pope Pius V, but James MacCaghwell (McCawell) was put forward by Elizabeth I of England.

FitzGibbon, who belonged to the royal Desmond family, being deprived of his see, fled to France and passed into Spain where he resided for a time at the Court.

Dermot O'Hurley, or Diarmaid Ó hUrthuile, of Limerick, a distinguished student of the university of Louvain in the Duchy of Brabant and professor at Reims in France, was appointed Archbishop of Cashel in 1581 by Pope Gregory XIII.

Having presided over the Roman Catholic diocese secretly for two years, he was discovered and brought before the Lord Justices at Dublin, was tortured upon his refusal to take the Oath of Supremacy to the English crown and was subsequently hanged outside the city on 20 June 1584.