Keyne was a pious virgin, one of the many daughters of King Brychan of Brycheiniog (Brecon). She may have lived at Keynsham in Somerset but founded St Keyne in Cornwall, (among other sites) in the late 5th century, and left her name to a church and to a well, the latter whose waters are said to give the upper hand to whichever of two newlyweds first drinks of them. In 490 she visited her nephew Saint Cadoc at St Michael's Mount, where a granite chair or throne supposedly is said to grant matrimonial advantage.
She died a virgin on 5 October in either 490 or 505, more likely the latter. She ... "grew up to be very beautiful, and many young men sought her hand in marriage, but she rejected them all."[who?] Her feast is celebrated on 8 October, although it is also recorded as 30 September.
She was the original patron of what is now St Martin-by-Looe (Penndrumm) and is linked with the River Kenwyn in Truro. She is known to have founded a few churches: Llangeinor in mid Glamorgan, Llangunnor and Llangain in Dyfed, at Rockfield (Llangennon), Runston, in Gwent ['Llan', in Welsh, means 'Holy Place (of...)'] and St Ceinwen's Church, Cerrigceinwen, where the churchyard encloses and Christianizes another holy well. She is also recorded as being a dragon-slayer, on par with St George.
The plaque next to the well describes the spell which Saint Keyne cast upon the water of the well. The plaque reads: "The legend of Saint Keyne Well. Saint Keyne was a princess who lived about 600 AD. She laid on the waters of this well a spell thus described by Carew in 1602 AD—'The quality that man or wife whom chance or choice attains first of this sacred spring to drink thereby the mastery gains.'"
Robert Southey's poem "The Well of St Keyne" recounts this legend.
- St Ceinwen's Church, Cerrigceinwen – a church in Anglesey dedicated to her
- Ray Spencer A Guide to the Saints of Wales and the Westcountry, pp. 51–52
- J. Meyrick A Pilgrim's Guide to the Holy Wells of Cornwall, pp. 68–69
- David Hugh Farmer Oxford English Dictionary of Saints
- "The Well of St. Keyne", Poemhunter