Petroc or Petrock (Medieval Latin: Petrocus; Welsh: Pedrog; French: Perreux; c. 468 – c. 564) was a British prince and Christian saint.

Probably born in South Wales, he primarily ministered to the Britons of Devon (Dewnens) and Cornwall (Kernow) then forming the kingdom of Dumnonia where he is associated with a monastery at Padstow, which is named after him (Pedroc-stowe, or 'Petrock's Place').

In Devon ancient dedications total a probable seventeen (plus Timberscombe just over the border in Somerset), mostly coastal and including one within the old Roman walls of Exeter as well as the villages of Petrockstowe and Newton St Petroc.

In Wales his name is commemorated at St Petrox near Pembroke, Ferwig near Cardigan and Llanbedrog on the Llŷn Peninsula.

[2] He founded a monastery and school at Lanwethinoc (the church of Wethinoc, an earlier holy man), at the mouth of the river Camel on the North Cornish Coast.

The place of his death was reputedly at a house belonging to a family named Rovel, thought to be a farm now called Treravel near Little Petherick.

As he set foot home in Britain under a heavy rain, he confidently told his companions that it would clear up by morning.

However, Henry II restored them and, though the relics were thrown out during the English Reformation, their ivory casket is still on public display at St. Petroc's in Bodmin.