Fintan (Munnu) of the moccu Moíe (d. 637), abbot of Tech Munnu (Taghmon, Co. Wexford) and defender of the Celtic Easter, was son of Tailchán or Tulchán, a member of the Cenél Conaill branch of the Northern Uí Néill. His father was a descendant of Fiachra Róede, whose descendants the Corca Raoidhe gave their name to the barony of Corkaree, Co. Westmeath, where Munnu founded the monastery of Taghmon before coming into Uí Chennselaig territory. His alias ‘Munnu’ is derived from the hypocoristic ‘mo Fhinnu’.
He first entered the monastic life at Achad Broan (probably in the barony of Corkaree, Co. Westmeath) under a priest named Grellán. He later studied under Comgall (qv) of Bangor, and finally at Daminis (Devenish, Co. Fermanagh). According to Adomnán (qv), he came to Iona after hearing of the death of Colum Cille (qv), who had prophesied his coming (‘Vita Columbae’, i. 2). He wished to enter the community, but was refused entry by Abbot Baíthéne (qv), acting under instructions given by Colum Cille before his death that Fintan should not be the monk of any abbot, but rather should be an abbot himself. Colum Cille had foreseen his greatness, and wished to see him fulfil his destiny as abbot of Taghmon in the present Co. Wexford. Fintan apparently remained for some time in Scotland, where he founded a number of churches in Argyll, which still bear his name.
When Fintan returned to Ireland, he founded the monastery of Taghmon in Co. Westmeath. He then travelled south into lands owned by the Uí Bairrche sept before they were supplanted by the Uí Chennselaig, where he entered a monastery named Aird Chrema, which was located in the townland of Hooks, parish of Kilcowan, Co. Wexford. Aird Chrema had close ties with Bangor, Co. Down, having been built on lands given to Bangor by a king of the Uí Bairrche. Fintan held the position of abbot for twelve years, but must have been a harsh disciplinarian as he was then asked (or told) to leave. On leaving, he called down a curse on his monks – possibly providing ammunition for Gerald of Wales (qv) who described Irish saints as being of a particularly vengeful disposition.
Fintan next moved to Achad Liathdroim, where he was given land by a chieftain named Dímma; it was later named after him as Tech Munnu (Taghmon). He remained there for the rest of his days, ruling with a rod of iron. Towards the end of his life he was afflicted with leprosy – a disease common enough in medieval Ireland, but according to tradition contracted by Fintan because of his harshness towards his monks. Fintan and his monastery achieved considerable fame, being mentioned in no fewer than seven Latin Lives of Irish saints, and in many other ecclesiastical, genealogical, and historical sources. Fintan himself is the subject of four extant Lives, all derived from a common original. Taghmon contained about 230 monks and lasted at least till 1060.
Fintan is said to have opposed the celebration of Easter according to the Dionysiac cycle accepted in Rome in the sixth century and agreed around 630 at the synod of the southern Irish churches at Mag Léne (near Durrow, Co. Offaly), which he pointedly refused to attend. He later attended the synod of Mag nAilbe and opposed the reforming views of Laisrén (qv) of Leighlin. In his letter (632/3) to Ségéne (qv) of Iona, Cummian Foto (qv) seems to refer to Fintan's meddling: ‘But a short time afterwards a certain whited wall arose, pretending to preserve the tradition of our elders, who did not unite with either part but divided them and partly made void what was promised. I hope the Lord shall strike him down in whatever way he wills’ (lines 272–3). The reference to a ‘whited wall’ (paries dealbatus) is probably a none-too-veiled allusion both to Fintan's leprosy and to his hypocritical dealings with his fellow ecclesiastics.
Fintan is commemorated by a number of foundations and dedications in Co. Wexford, particularly in the parishes of Taghmon, Ishartmon, Ballymore and Tacumshin. The Irish martyrologies note his feast-day on 21 October; the Breviary of Aberdeen has a lesson for his feast-day. He is sometimes confused with the Scottish saint Mundus.