Berchán (6th cent.?), founder and first abbot of Cluain Sasta (Clonsast, Co. Offaly) and saint in the Irish tradition, appears to be at the centre of an extensive network of interlocking cults. The genealogies represent him as the son of Muiredach son of Daig and of Fiamain daughter of Diarmait, linking him to Dál Riata of Scotland on his father's side and to Cenél Lóeguire on that of his mother. By implication, therefore, he is to be identified with the ‘prophet’ Berchán, to whom various Middle Irish ‘prophesies’ are attributed, including an account of kings of Ireland down to the twelfth century. The genealogies of the Irish saints include at least eleven individuals named Berchán, several of whom are clearly duplications. One of these, attached to the Leinster dynasty of Dál Messin Corb and placed at Senchill (Shankill, Co. Dublin), is apparently associated with Cóemgen (qv) of Glendalough. It may well be that separate personae of the saint were cultivated in each of the four provinces as the cult diffused; the cult of Berchán was also widespread in medieval Scotland. It is possible that in some instances confusion arose between like-named saints, some of whom, notably Berach (qv) of Cluain Coirpthe and Berchán (qv) (Mo-Bí) of Glasnevin, probably had an historical existence.
Berchán of Cluain Sasta is said to have been a bishop. He is commemorated in the Martyrology of Tallaght at 4 August and in the other Irish martyrologies at 4 December. A certain Ciarán of Cluain Sasta (if he is not an alter ego of Ciarán (qv) (c.512–45) of Clonmacnoise), noted in the Martyrology of Tallaght at 30 April, may have been a colleague and/or successor of Berchán. It appears likely that aunts of Berchán, the daughters of Diarmait, were also commemorated at Cluain Sasta.