St. Odilo was a little man, of insignificant appearance and immense force of character; under him Cluny was at its greatest. Already in the days of St. Berno, Cluny had been something more than the normal self-governing institution envisaged in the Rule of St. Benedict. It had been linked with the abbey of Baume by St. Berno, who intended the union to continue. The idea was that each should help the other to maintain proper Benedictine practice. At the same time, the early abbots of Cluny were constantly called to reform other monasteries which, however, preserved their independence once the reform was complete. In many cases nothing further was needed—the English monastic reform undertaken by SS Dunstan, Ethelwold and Oswald under Cluniac influence is a conspicuous instance of Cluny's success by example—but many reformed communities soon slipped back into their old ways. St. Odilo sought to prevent this by extending the original connection between Baume and Cluny very much further. He no longer merely reformed monasteries but subjected them permanently to Cluny; he appointed every prior of every Cluniac house, and the profession of every monk in the remotest monastery was made in his name and subject to his sanction. He periodically visited the monasteries subject to Cluny and saw to it that discipline was strict.
Fifth Abbot of Cluny . 962; d. 31 December, 1048. He was descended from the nobility of Auvergne. He early became a cleric in the seminary of St. Julien in Brioude. In 991 he entered Cluny and before the end of his year of probation was made coadjutor to Abbot Mayeul, and shortly before the latter's death (994) was made abbot and received Holy orders. The rapid development of the monastery under him was due chiefly to his gentleness and charity, his activity and talent for organizing. He was a man of prayer and penance, zealous for the observance of the Divine Office, and the monastic spirit. He encouraged learning in his monasteries, and had the monk Radolphus Glaber write a history of the time. He erected a magnificent monastery building, and furthered the reform of the Benedictine monasteries. Under Alphonse VI it spread into Spain. The rule of St. Benedict was substituted in Cluny for the domestic rule of Isidore. By bringing the reformed or newly founded monasteries of Spain into permanent dependence on the mother-house, Odilo prepared the way for the union of monasteries, which Hugo established for maintaining order and discipline. The number of monasteries increased from thirty-seven to sixty-five, of which five were newly established and twenty-three had followed the reform movement. Some of the monasteries reformed by Cluny, reformed abbey; thus the Abbey of St. Vannes in Lorraine reformed many on the Franco-German borderland. On account of his services in the reform Odilo was called by Fulbert of Chartres the "Archangel of the Monks", and through his relations with the popes, rulers, and prominent bishops of the time Cluny monasticism was promoted. He journeyed nine times to Italy and took part in several synods there. John XIX and Benedict IX both offered him the Archbishopric of Lyons but he declined. From 998 he gained influence with the Emperor Otto III. He was on terms of intimacy with Henry II when the latter, on political grounds, sought to impair the spiritual independence of the German monasteries. For Germany the Cluny policy had no permanent success, as the monks there were more inclined to individualism. Between 1027 and 1046 the relations between the Cluniac monks and the emperor remained unchanged. In 1046 Odilo was present at the coronation of Henry III in Rome. Robert II of France allied himself with the Reform party.
The conclusion of the Peace of God (Treuga Dei), for which Odilo had worked from 1041, was of great economic importance. During the great famines of that time (Particularly 1028-33), he also exercised his active charity and saved thousands from death.
He established All Souls Day (2 November) in Cluny and its monasteries (probably not in 998 but after 1030, and it was soon adopted in the whole church. Of his writings we have but a few short and unimportant ones: a life of the holy Empress St. Adelaide to whom he was closely related; a short biography of his predecessor Mayeul; sermons on feasts of the ecclesiastical year; some hymns and prayers; and a few letters from his extensive correspondence.
Odilo and his confreres interested themselves in the church reform which began about that time. They followed no definite ecclesiastico-political programme, but directed their attacks principally against individual offences such as simony, marriage of the clergy, and the uncanonical marriage of the laity. The Holy See could depend above all on the religious of Cluny when it sought to raise itself from its humiliating position and undertook the reform of the Church.
He died while on a visitation to the monastery of Souvigny where he was buried and soon venerated as a saint. In 1063 Peter Damien undertook the process of his canonization, and wrote a short life, an abstract from the work of Jotsald, one of Odilo's monks who accompanied him on his travels. In 1793 the relics together with those of Mayeul were burned by the revolutionaries "on the altar of the fatherland". The feast of St. Odilo was formerly 2 January, in Cluny, now it is celebrated on 19 January, and in Switzerland on 6 February.