The first Bishop of Clermont was St. Austremonius (Stramonius). According to local tradition he was one of the seventy-two Disciples of Christ, by birth a Jew, who came with St. Peter from Palestine to Rome and subsequently became the Apostle of Auvergne, Berry, Nivernais, and Limousin. At Clermont he is said to have converted the senator Cassius and the pagan priest Victorinus, to have sent St. Sirenatus (Cerneuf) to Thiers, St. Marius to Salers, St. Nectarius and St. Antoninus into other parts of Auvergne, and to have been beheaded in 92. This tradition is based on a life of St. Anstremonius written in the tenth century in the monastery of Mozac, where the body of the saint had rested from 761, and rewritten by the monks of Issoire, who retained the saint's head. St. Gregory of Tours, born in Auvergne in 544 and well versed in the history of that country, looks upon Austremonius as one of the seven envoys who, about 250, evangelized Gaul; he relates how the body of the saint was first interred at Issoire, being there the object of great veneration.
Clermont counted amongst its bishops a large number of saints, as St. Urbicus (c. 312); St. Leoguntius; St. Illidius (Allyre), who, about 385, cured the daughter of the Emperor Maximus at Trier; the saint's name was given to the petrifying springs of Clermont, and his life was written by Gregory of Tours; St. Nepotianus (died 388); St. Artemius (died about 394); St. Venerandus (Veau, died about 423); St. Rusticus (424-46); St. Namatius (446-62), founder of the Clermont cathedral, where he deposited the relics of St. Vitalis and St. Agricola brought from Bologna; Sidonius Apollinaris (470-79), the celebrated Christian writer who brought to Clermont the priest St. Amabilis; St. Aprunculus (died about 491); St. Euphrasius (491-515); St. Quintianus (died about 527), whose life was written by Gregory of Tours; St. Gallus (527-51), of whom Gregory of Tours was the biographer and nephew; St. Avitus (second half of the sixth century), founder of Notre Dame du Port; St. Cæsarius (c. 627); St. Gallus II (c. 650); St. Genesius (c. 660); St. Præjectus (Prix), historian of the martyrs of Clermont and assassinated at Volvic 25 January, 676; St. Avitus II (676-91); St. Bonitus, intimate friend of Sigebert II (end of seventh century); St. Stabilis (823-60). and St. Sigo (866).
Among the Bishops of Clermont should also be mentioned: Pierre de Cros (1301-04), engaged by Thomas Aquinas to complete his Summa; Etienne d'Albert (1340-42), later Pope Innocent VI (1352-62); Guillaume du Prat (1528-60), founder of the Clermont College at Paris and delegate of Francis I of France to the Council of Trent; and Massillon, the illustrious orator (1717-42). The Diocese of Clermont can likewise claim a number of monks whom the Church honours as saints, viz: St. Calevisus (Calais, 460-541), a pupil in the monastery of Menat near Riom, whence he retired to Maine, where he founded the Abbey of Anisole; St. Maztius (died 527), founder at Royat near Clermont of a monastery which became later a Benedictine priory; St. Portianus (sixth century), founder of a monastery to which the city of Saint-Pourçain (Allier) owes its origin; St. Etienne de Muret (1046-1124), son of the Viscount of Thiers and founder of the Order of Grandmont in Limousin, and St. Peter the Venerable (1092-1156), of the Montboissier family of Auvergue, noted as a writer and Abbot of Cluny.
Several famous Jansenists were natives of Clermont: Blaise Pascal, author of the Pensées (1623-62); the Arnauld family, and Soanen (1647-1740), Bishop of Senez, famous for his stubborn opposition to the Bull "Unigenitus". On the other hand the city of Riom was the birthplace of Sirmond, the learned Jesuit (1559-1651), confessor to Louis XIII and editor of the ancient councils of Gaul. Other natives worthy of mention in church history were the Abbé Delille, poet (1738-1813), and Montlosier, the publicist (1755-1838), famous for his memoir against the Jesuits and to whom Bishop Ferou refused ecclesiastical burial.
Pope Urban II came to Clermont in 1095 to preside at the organization of the First Crusade; Pope Paschal II visited the city in 1106, Callistus II in 1120, Innocent II in 1130, Pope Alexander III in 1164, and, in 1166, Thomas Becket. It was also at Clermont that, in 1262, in presence of St. Louis, the marriage of Philip the Bold and Isabella of Aragon was solemnized.