Saint Cwyllog (or Cywyllog)[1] was a Christian holy woman who was active in Anglesey, Wales, in the early 6th century. The daughter, sister and niece of saints, she is said to have founded St Cwyllog's Church, Llangwyllog, in the middle of Anglesey, where a church is still dedicated to her.
- ^ Baring-Gould, p. 279.