Brigid of Kildare is, with Patrick and Columba, one of the three patron saints of Ireland. She founded the monastery of Kildare — probably a double house of men and women — which became one of the most important centers of Irish Christianity. Her historical existence is virtually certain, but separating the real Brigid from the legendary one is exceptionally difficult: her hagiography absorbed elements from a pre-Christian Irish goddess of the same name, and the early Lives are saturated with miraculous material that owes more to Irish mythological tradition than to historical reporting. What emerges through the legends is a figure of extraordinary generosity, hospitality, and practical leadership.

Brigid is the subject of extensive hagiographic tradition. According to Cogitosus and later Lives, she was born of a mixed marriage, vowed virginity, founded Kildare with astonishing speed, performed countless miracles (healings, multiplications of food, exorcisms), and established the perpetual flame. In Irish folklore, Brigid is often conflated with the pre-Christian goddess Brigid.

The historical core of Brigid's life is frustratingly thin. She was born around 451, probably in Leinster, and was associated with Kildare ('Church of the Oak') from an early stage. The monastery she founded there became a major ecclesiastical center — Cogitosus, writing her earliest Life around 650, describes a grand church with elaborate decoration and a thriving double community of monks and nuns.

Brigid's foundation at Kildare was unusual in the early Irish church for the authority she exercised. Cogitosus describes her as governing both the women's and men's communities, and later tradition credited her with quasi-episcopal authority — a bishop was attached to her community, but it was Brigid, not the bishop, who was the true power. This has led some scholars to see Kildare as evidence for women's ecclesiastical authority in the early Celtic church, though others caution against reading too much from hagiographic sources.

What is clear is that Kildare, under Brigid's leadership and that of her successors, became one of the wealthiest and most influential churches in Ireland. The Book of Kildare, a lavishly illuminated gospel book now lost, was described by Giraldus Cambrensis in the twelfth century as a work of almost supernatural beauty.

• Monastic