St Meriasek (Meriadek in Breton) was a 4th century Celtic Christian saint. The legends of his life are known through Beunans Meriasek , a Cornish language play completed in 1504, and a few other sources. He is the patron saint of Camborne, and according to his legendary will his feast day is the first Friday in June.

Meriasek was a Breton from a ducal family. Conan Meriadoc, the legendary king of Brittany at the time, wanted to arrange a political marriage for him; but Meriasek preferred to renounce his inheritance and become a priest. He crossed the Channel to found an oratory in Camborne, Cornwall.

Encountering persecution, he returned to Brittany to found a chapel in Josselin, in the lands of the Earls of Rohan. Meriasek is reputed to have healed many lepers and disabled people, to have driven off the highwaymen of Josselin through prayer, to have made water spring from solid rock, and to have calmed a storm.

He was elevated to become bishop of Vannes but continued to wear a hair shirt, practise asceticism, and minister to the poor. His sacred well in Camborne was long thought to have the power of healing the insane.