Saint Kieran (aka St. Ciaran) 516-549 was born in Roscommon, Connacht. Kieran left his boyhood home to study at the famous monastery at Clonard in Meath. From there he went to Aranmore in Galway Bay, where, like most contemporary saints, he communed with the Holy Abbot Enda. One night, the two men had a shared vision of a great tree, heavy with fruit, by a stream in the middle of Ireland. Enda interpreted this to mean that Kieran should go and search for such a place and establish a church there.

Obeying the vision, Kieran eventually settled at Clonmacnoise, County Offaly, on the Shannon River. The monastery founded 548 on the site by St. Kieran became the most famous in Ireland which attracted scholars from all over Europe. Kieran did not direct the monastery for long, however, as he died of a plague in early middle life.

Despite Viking raids and a dozen major fires, the monastery survived for 1,000 years until it was destroyed by the English in 1552. Notable ruins include a cathedral built in 904, several churches, two round towers, three sculptured crosses, over 200 inscribed stones, and a castle built in 1214. The ruins comprise a national monument.

The annual feast of Saint Kieran is held at Clonmacnoise on September 9th.