and that his nephew, St. Mel (died c.490), was its bishop or abbot. Although there is no historical or archaeological evidence to support it, Mel is regarded as the founder of the see.

The diocese of Ardagh was established in 1111 at the Synod of Rathbreasail as the see for east Connacht. At the subsequent Synod of Kells in 1152, its area was reduced to the territory of the Conmaicne.