Saint Brioc (also known in French as Brieuc, and in Breton as Brieg) was an early 6th century Welshman who became the first Abbot of Saint-Brieuc in Brittany.

Very little is known about his early life, as his 9th century 'life' is not altogether reliable. James Ussher, the 17th century Primate of All Ireland, says that the saint was of Irish birth. However, there is no evidence for this assertion and his life states that he came from Ceredigion where, indeed, he has a church at Llandyfriog. He is supposed to have studied under 'Germanus of Paris', but whether this is supposed to be Saint Germanus of Auxerre or Germanus of Paris is unclear. According to his 'life', he performed miracles even before ordination. He founded the church of St Breock in Cornwall, but eventually settled in Brittany where he founded a monastery at Landebaeron. He then went to upper Brittany and established an oratory at a place still referred to as St Brieuc-des-Vaux. He was made the first bishop of the diocese now called Saint-Brieuc. The 'life' provides details of many miracles, including a cure of Count Riguel, who donated to him his palace at Champ-du-Rouvre and estates in gratitude.

Brioc died in his monastery at St Brieuc-des-Vaux and was interred in his cathedral church there, which was dedicated to Saint Stephen. His relics were translated to Angers in 865 and translated again in 1166. A portion of the relics, as well as his ring, was given back to St Brieuc Cathedral in 1210. His feast day is 1 May.