According to local mythology, the Rock of Cashel originated in the Devil's Bit, a mountain 20 miles north of Cashel, when St. Patrick banished Satan from a cave, resulting in the Rock's landing in Cashel. Cashel is reputed to be the site of the conversion of the King of Munster by St. Patrick in the 5th century.

The Rock of Cashel was the traditional seat of the kings of Munster. In 1101, King Muirchertach Ua Briain donated it to the Church. The oldest of the buildings is the round tower, dating from 1101. The chapel of King Cormac Mac Carthaigh was consecrated in 1134. It is the finest Romanesque church in Ireland. The Cathedral dates from 1235.