Saint Theuderius (or Theuderis, Theudar, Theodore, Cherf, Chef, French: Theudère de Vienne; died c. 575) was a Christian monk, abbot and hermit.

Chef, a young gentleman of one of the best families of the city of Vienne, by the interior call of the Holy Ghost, forsook the world; and having long exercised himself in the most perfect practices of a monastic life under the direction of Saint Cæsarius at Arles, returned to his own country, and being joined by several disciples, built for them first cells, and afterwards a monastery near the city of Vienne in Dauphine.

It was anciently a custom in the most regular monasteries, that the hebdomadarian priest who said the community mass, spent the week in which he discharged that function, in the closest retirement in his cell, and in holy contemplation and austere penance, both that he might be better prepared to offer daily the tremendous sacrifice, and that he might more faithfully acquit himself of his mediatorship between God and his people.

It was also a peculiar custom at Vienne in the sixth century, that some monk, of whose sanctity the people entertained a high opinion, was chosen, who should voluntarily lead the life of a recluse, being walled up in a cell, and spending his whole time in fasting, praying, and weeping to implore the divine mercy in favour of himself and his country.

Saint Chef was pitched upon for this penitential state, which obligation he willingly took upon himself, and discharged with so much fervour as to seem desirous to set no bounds to his tears and mortifications.

His relics were translated to a collegiate church of which he is the titular patron, and which gives the name of Saint Chef to the town where it stands, in Dauphine, eight leagues from Vienne.

[8] Jacques Longueval (1680–1735) wrote in his Histoire de l'église gallicane, Theuderius, commonly called Saint Cherf, came from a noble family in the province of Vienne.

Theuderius, after having perfected himself in the practice of Christian virtues, returned to Vienne, where he first built a small oratory near the city in honor of Saint Eusebius of Vercelli.

The position having become vacant, Philippe, bishop of Vienne, cast his eyes on Saint Theuderius, and enclosed him in a cell near the church of Saint-Laurent.