Saint Carantoc (also known in Welsh as Carannog, Irish as Cairnech, Breton as Karanteg, Latin as Carantocus, corrupted English as Carantock, and other variations) was a confessor and abbot of the early 6th century in Wales and what is now the English West Country.

Many details of his life are obscure or contradictory. He was either a son of Ceredig or his son, Corun, King of Ceredigion. To escape being elected king, he fled to Llangrannog. The shavings he produced for lighting a fire there were carried away as soon as they were made by a dove. Where the bird alighted, Carantoc built the present church. This story is sometimes ascribed to Crantock in Cornwall, where the parish church is dedicated to Saint Carantoc, but according to his life in the Leon Breviary, this was definitely in Wales. He probably moved to Cornwall before preaching for some time in Ireland, around Dulane in County Meath and Inis-Baithen in Leinster. According to the 'Vita Carantoci' this was under the instruction of Saint Patrick, but this does not fit chronologically with other aspects of his life. It is also sometimes said that he spent time in Brittany, but the stories of his time there replicate those from Britain.

In the most famous incident of Carantoc's life, the saint, having returned to Wales, crossed the Bristol Channel, looking for his portable altar. He arrived on the banks of the River Willett and came into conflict with both King Cado of Dumnonia and King Arthur at Dunster in Somerset. He was eventually obliged to defeat a ferocious dragon in order to retrieve his altar and, in return, was given land at nearby Carhampton to found a monastery.

Carantoc's place of death and burial is disputed between Inis Baithen and Dulane. His feast day is 16 May.