| Ffynnon Gwenfaen | |
|---|---|
| St Gwenfaen's Well | |
.jpg) Remains of well building | |
| Type | holy well |
| Location | Anglesey, Wales |
| Coordinates | 53°14′49″N 4°36′36″W / 53.247°N 4.610°W |
| OS grid reference | SH 2595 7544 |
| Official name | Ffynnon Gwenfaen |
| Designated | 16 July 1987 |
| Reference no. | AN055 |
Listed Building – Grade II | |
| Official name | Ffynnon Gwenfai |
| Designated | 5 April 1971 |
| Reference no. | 5328 |
  Location in Anglesey | |
St Gwenfaen's Well (also known as Welsh: Ffynnon Gwenfaen, Welsh: Ffynnon Wenfaen and Welsh: Ffynnon Gwenfai) is an early medieval holy well in the south west of Holy Island, Anglesey, named after St Gwenfaen, whose cloister was nearby. The site includes substantial remains of a building and is both a scheduled monument and a Grade II listed building. Traditionally, a gift of two white quartz pebbles thrown into the pool can cure mental health problems.