12th Century Reorganisation

In the early 12th century Muirchertach Mor O'Briain was leader of the Dal gCais and could be regarded as High King, although he never got full recognition in the northern half of the country. Muirchertach gave his support to the movement for reform and was present at the Synod of Rathbreasail in 1111 which divided Ireland into dioceses for the first time. The king's influence and power were apparent in the huge amount of territory given to the diocese of Killaloe, streching from Loop Head in the west to Kinnity in the east. Following the death of Muirchertach in 1119 the power of the O'Briens declined and this gave an opportunity to the outlying areas of the new diocese of Killaloe to assert their independence. As a result, when another national synod was held in Kells in 1152 at which the arrangement of dioceses was reconsidered, the diocese of Killaloe was reduced considerably in size. Roscrea (in the east) and Iniscathaig (in the west) were now recognised as independent dioceses. At Kells the diocese of Kilfenora was also given recognition, embracing the baronies of Corcomroe and Burren.

Iniscathaig was an unusual diocese as it had territory north and south of the Shannon. It did not maintain its independence for long. There was a resurgence of O'Brien power under Donal Mor O'Briain, King of Thomond from 1168 to 1194. Once again the outlying areas were absorbed into Killaloe diocese, including the part of Iniscathaig north of the Shannon. Its last bishop, Aed Ua Beccan, died in 1188.

Donal Mor O'Briain took a strong interest in church affairs and was associated with new religious foundations at Clareabbey, Inchicronan, Canon's Island, Killone (the only known convent of nuns in Killaloe diocese in medieval times) and Corcomroe (in Kilfoenora diocese). The present cathedral of St. Flannan in Killaloe (now Church of Ireland) seems to date from the early 13th century. Howeve, the fine Hiberno-Romanesque doorway which is built into the south wall of the cathedral almost certainly goes back to the reign of Donal Mor and the episcopate of his brother, Constantin O'Briain (Bishop of Killaloe, 1168 - 1194). The cathedral in Kilfenora, which is still used by the Church of Ireland, also dates from the end of the 12th century.

The patron of Killaloe diocese is St. Flannan, whose feast is on 18 December. The medieval life of St. Flannan is now regarded as historically valueless and we have little hard information about him. It would appear that he lived in the 8th century, possibly in West Clare. The prominence given to him was due to family pride on the part of the kings of the Dal gCais in the 11th and 12th centuries. They were glad to have a saint as a family member and were determined to give him due honour. The 12th century Latin life provided biographical details which were accepted uncritically until recent times. Two days after the feast of St. Flannan, we have the feast of St. Fachanan (20 December), patron of Kilfenora diocese. Again, little is known about him but he is associated with the foundation of the first monastic settlement in Kilfenora.