St Patrick's Island, known in Irish as Inis Phádraig, was the home of a monastic community associated with a figure called Mochonna, a 7th-century saint venerated on the 13th of January. The unusual thing about Mochonna is just how slippery the name turns out to be. According to the scholar Pádraig Ó Riain, writing in 2011, the name was one of at least twenty-eight variant forms derived ultimately from Colum, the most significant holy name in early Christian Ireland. Mochonna, Dochonna, Mochonóg, Conna, and several palatalized variations were all, in essence, pet forms of the same root name, applied to different local saints across the island. It has even been suggested that Dochonna of this very island and Colmán Briot, founder of Gallen monastery in County Offaly, were one and the same person.

The monastery's documented history is fragmentary but vivid where it does survive. The Annals of Ulster record that in 797 AD the island was burned by Vikings, who also carried off livestock from the surrounding district and, crucially, broke the shrine of Dochonna. A reliquary shrine of this kind would have been a decorated metal container housing the saint's relics, both spiritually and politically significant to the community that kept it. The destruction of such an object was not incidental damage but a deliberate act. A later figure, Maol Finniain, is recorded by the medieval martyrologist Maol Muire Ua Gormáin as abbot of Inis Phádraig and commemorated on 6 February. Intriguingly, the obit of Maol Finniain son of Flannagán, king of Breagha, a territory roughly corresponding to modern Meath with parts of Dublin and Louth, who died in 903, describes its subject as a 'religious layman'. The coincidence of names has led some to wonder whether a king and an abbot were, somehow, the same man.

The island lies off the coast north of Dublin and is not easily accessible. Aerial photography has revealed traces of a roughly circular enclosure surrounding the church remains, the kind of curvilinear boundary typical of early Irish monastic sites, where the enclosed ground was considered sacred and legally protected. The church and enclosure are recorded in the Sites and Monuments Record for Dublin. Anyone with a serious interest in early medieval ecclesiastical landscapes will find the aerial photography more legible than a visit, given the difficulties of access, but the wider coastal setting of Inis Phádraig gives some sense of why an early monastic community might have chosen it: isolated enough for contemplation, close enough to the mainland to remain connected to the political world of Breagha and beyond.