céli Dé, ‘clients of God’ (often Anglicized as ‘culdees’), was the name adopted by reforming ascetics in Ireland in the late 8th and early 9th cents. Based primarily in southern Irish monasteries such as Tallaght and Lismore, they sought to renew the monastic life-style of devotion, prayer, and asceticism. They were also keenly interested in wider structural reform, such as the provision of proper pastoral care.

Diarmait, abbot of Iona 814–c.831, was influential on the reformers, who looked to early founders like Columba as models of monastic behaviour. It may be Diarmait who helped to introduce the céli Dé to Scotland, where they were singularly successful. By c.940 there was a céli Dé community in St Andrews, where the Scottish king, Constantine son of Æd, retired into religion as their head. Through charters and church documents of the 11th cent. and later, we know of communities also in Abernethy, Brechin, Dunblane, Iona, probably Dunkeld, and many other monasteries.

The céli Dé lived in communities apart from the larger monastic or cathedral setting, in essence a monastery within a monastery. Although the membership of the community would appear to have been partly hereditary (members becoming celibate only later in life, upon entering strict observance), in places such as Kells in Ireland, the céli Dé were the observant monastics in an otherwise largely commercial and administrative religious power-centre. In Scotland, they continued to staff monasteries which did not change to continental rules, although many eventually became Augustinian canons. Some conflict is observable between newly introduced orders and the entrenched and conservative céli Dé, especially in St Andrews. Though tenacious, both communities and terminology gradually became obsolete in the course of the later Middle Ages.

Thomas Owen Clancy