Saint Petroc (sometimes spelt Petrock in English, Pedrog in Welsh and Perreux in French) (d. 564) is a 6th century Celtic Christian saint. He was born in Wales but primarily ministered to the Britons of Dumnonia which included the modern counties of Devon (Dewnans), Cornwall (Kernow), and parts of Somerset (Gwlas an Hav) and Dorset. He is also known to have ministered to the people of Brittany.

Early life
Old Welsh genealogies record that he was a younger son of King Glywys Cernyw of Glywysing (now Glamorgan), and there are local dedications to him at St Petrox near Pembroke and Ferwig near Cardigan. He has also given his name to Llanbedrog, a village on the Lleyn peninsula. He studied in Ireland (where he was the teacher of Saint Kevin).

Travels
After studying, he began his mission to Cornwall, where he founded monasteries at Padstow and Bodmin. Padstow, which is named after him (Pedroc-stowe, or 'Petrock's Place'), appears to have been his base for some time. There are numerous other dedications to him throughout Cornwall and he is even said to have converted its king, Constantine of Dumnonia, to Christianity. After thirty years, legend says that he went on the pilgrimage to Rome by way of Brittany.

Upon his return, Petroc passed through Devon, where ancient dedications to him are even more numerous: a probable seventeen (plus Timberscombe just over the border in Somerset), compared to Cornwall's five. The position of churches bearing his name, nearly always near the coast, reminds us that in those days travelling was done mainly by sea. The North Devon towns of Petrockstow and Newton St Petroc are also named after Saint Petroc and the popularly-adopted unofficial flag of Devon is dedicated to him.

The legendary tales surrounding Petroc are exceptionally vivid and imaginative (giving him a second pilgrimage, travels to India, taming wolves) and may represent interpolation from pagan tales.

Veneration
In iconography, Petroc is usually shown with a stag. His feast day is June 4. His major shrine was always at St Petroc's Church, Bodmin. In 1177, a Breton stole his relics from Bodmin and gave to the Abbey of St Meen. However, Henry II restored them and, though the relics were thrown out during the English Reformation, their beautiful ivory casket is still on public display in the church. With Saint Piran and Saint Michael, he is patron saint of Cornwall.