Saint Dubricius (also known in his native Welsh as Saint Dyfrig and in corrupt Norman-French as Saint Devereux) was the 6th century evangelist of Ergyng and much of South Wales.

Dubricius was the illegitimate son of Efrddyl, the daughter of King Peibio Clafrog of Ergyng (modern West Herefordshire in England). His grandfather threw his mother into the River Wye when he discovered she was pregnant, but was unsuccessful in drowning her. Dubricius was born in Madley. He and his mother were reconciled with Peibio when Dubricius kissed him and cured him of his leprosy.

Dubricius founded a monastery at Hentland and then one at Moccas. He became the teacher of many well-known Welsh saints, including Teilo and Samson. Dedications at Porlock and near Luscombe on the Exmoor coast of Somerset may indicate that he also travelled in that area. He later became Bishop of Ergyng, possibly with his seat at Weston-under-Penyard, and probably held sway over all of Glamorgan and Gwent, an area that was later known as the diocese of Llandaff. However, he may have merely been a bishop for the purpose of ordaining priests, not as administrative head of the church over a geographical area. Dubricius was good friends with Saints Illtud and Samson, and attended the Synod of Llanddewi Brefi in 545, where he is said to have resigned his see in favour of Saint David. He retired to Bardsey where he was eventually buried before his body was transferred to Llandaff Cathedral in 1120.

According to legend, Dubricius was made Archbishop of Wales from Caerleon by Saint Germanus of Auxerre, and later crowned King Arthur. He appears as a character in Geoffrey of Monmouth's Historia Regum Britanniae, and, much later, in Alfred, Lord Tennyson's Idylls of the King. Arthurian scholar Norma Lorre Goodrich, in her book Merlin, controversially claims that St Dubricius and Merlin were the same person, Merlinus Ambrosius Dubricius, who was born in 450, and died in 536.