He was a native of Gaul, and flourished towards the end of the fifth age. After the death of his parents, who were Christians, he distributed all his substance to the poor; and, in order to serve God with more ease, retired into a desert, where the bishop of the place, discovering his merit, ordained him a deacon.
He then determined to consecrate himself entirely to the ministry of the word; and having preached in several provinces of Gaul, he came into the territory of Chartrain, where he found but a small number of Christians, the descendants of those who had been formerly converted by Saint Potentianus and Saint Altinus. The gospel having made a rapid progress by his zeal, he made choice of some disciples to assist him in extending the knowledge of Jesus Christ; and set out on his way to Paris.
He had scarcely advanced three leagues from Chartres when he perceived a gang of robbers approaching towards him; whereupon he advised his disciples to hide themselves among the thickets while he would amuse the robbers by discoursing with them. These savages, provoked at not finding any money in his possession, fell upon him and inhumanly murdered him. Thus died Saint Caraunus, a martyr of charity.
His disciples buried his body near Chartres, upon an eminence which was since called the Holy Mount; and after some time a church was erected there under his invocation, the care of which was entrusted to a community of ecclesiastics; but the canon regulars were substituted in their room in 1137. The relics of Saint Caraunus are kept in the abbey of his name near Chartres. The president of Lamoignon obtained one bone of them in 1681, for the church which is dedicated to the saint at Mont-couronne, one of the parishes of Baville. His name is mentioned on this day in the Martyrologies; and the feast of his translation is kept at Chartres on the 18th of October.