Bruno di Segni (c. 1045 – 18 July 1123) was an Italian Roman Catholic prelate and professed member from the Order of Saint Benedict who served as Bishop of Segni and Abbot of Montecassino. He studied under the Benedictines in Bologna before being appointed a canon of the cathedral chapter of Siena. He was invited to Rome, where he became a bishop and counseled four consecutive popes. He served as Abbot of Montecassino but when he criticised Pope Paschal II regarding the Concordat of Ponte Mammolo in 1111 the pope relieved him of his duties as abbot and ordered Bruno to return to his diocese, where he died just over a decade later. Bruno's canonization was celebrated on 5 September 1181 under Pope Lucius III, who presided over the celebration in the late bishop's diocese.
Bruno was born circa 1045 in Solero either to nobles or parents of modest means named Andrea and Guglielmina. He spent his theological education in the Benedictine house of Santa Perpetua near his town in Asti and at the University of Bologna where he also studied humanities and the liberal arts. It was around this time that he wrote one of his earliest works, Expositio in psalterium Gallicanum, dedicated to his bishop, Ingo of Asti (1072-1079). Bruno became a canon in Siena in 1073, and recollects his life among the canons; perhaps his ordination to the priesthood is to be located in the same period, and around that time was assigned as a pastor there. This happened after he decided to enter the Abbey of Montecassino to be a monk, but during the trip, he fell ill in Siena, where he remained subject to the needs of Bishop Rudolfus (1073–1083), who named Bruno as a canon of the cathedral Chapter.
Bruno became noted for his defending orthodoxy and for his extensive knowledge of Sacred Scripture and great piety. He was in Rome in 1079, and participated in the Sixth Roman Synod of Pope Gregory VII in February 1079. He was one of those who spoke on the floor of the Synod on the theory of transubstantiation and the theology of the Blessed Sacrament, against the teaching of Berengarius of Tours; at the synod, Berengarius renounced his heresy and was absolved by Pope Gregory. In Rome he was a guest of Pietro Igneo, the Bishop of Albano. Pope Gregory appointed the Bishop of Albano to go to Segni with Bruno, and to persuade the canons of the cathedral Chapter to elect Bruno as their bishop. Bruno was appointed as the Bishop of Segni In 1079, after the canons of the cathedral of Segni selected him. Pope Gregory VII himself, a good friend of Bruno who often sought his counsel, consecrated him a bishop.
According to Peter the Deacon, when the previous bishop of Segni, Erasmus, came to die, the pope asked Bruno to step in as administrator of the Church of Segni. As is traditional in such cases, Bruno pleaded his unworthiness and attempted to refuse. The pope was determined, however, and Bruno set off for Segni. In the meantime, the pope sent a mitre to the leaders of the church at Segni, ordering them to have Bruno consecrated as their bishop. When Bruno realized what was going on, he attempted to flee. Still, on the road in the middle of the night, he met a lady dressed in imperial regalia whose face shone like the sun (a personification of the Church of Segni), who chided him for fleeing from his bride. Struck by this, Bruno returned and allowed himself to be consecrated bishop.
During May and June 1081, the Emperor-elect Henry IV brought his army and his Clement III (Wibert of Ravenna) to the neighbourhood of Rome, and besieged the city. He had to withdraw to the north in the summer, but next year he returned and spent the entire Lenten season. At one of these times, Bruno was travelling from Segni to Rome when Adolfo di Segni, a supporter of Henry IV, who was ambitious to become Lord of Segni in place of the bishop, seized and imprisoned Bruno for three months. He was freed and returned to Rome. King Henry returned at the end of 1082 for a seven-month siege, during which fierce fighting in and around the Leonine City forced Pope Gregory to seek refuge in the Castel Sant' Angelo. Bruno was imprisoned once more, in the Castel Sant'Angelo alongside the pope. Hartmuth Hoffmann remarks that it is doubtful that during the following decade, he would have had the opportunity to deal with his own diocese as usual.
Bishop Bruno of Segni attended the eighth Roman synod of Pope Gregory VII, on 4 May 1082.
Pope Victor III (1086–1087) named him the Librarian of the Holy Roman Church, and he held the position until he left for Montecassino in 1099. By 1 July 1089, Cardinal Giovanni Gaetani, Cardinal Deacon of S. Maria in Cosmedin, was papal chancellor.
Pope Urban II was elected on 12 March 1088. Bishop Bruno accompanied Pope Urban on his tour of southern Italy, and was present at Salerno on 14 January 1093, where he subscribed a grant of privileges to Abbot Peter of Cava. On 24 August 1093, he was present at the monastery of S. Maria de Panso, a dependency of Montecassino, where the pope consecrated the major church, and Bruno consecrated the chapel in the cloister. He subscribed a papal document dated 6 February 1094 at Santa Maria Nuova in Rome; he also subscribed on 19 March and 5 April.
In 1095, Pope Urban was invited by Countess Matilda of Tuscany to visit her domains. Urban held a council at Piacenza during the first week of March, and was gratified and encouraged by the reception he received from every quarter. He was determined to carry his crusade into France, his homeland. Bruno had connections to Pope Urban II, and is found in the papal entourage at Tarascon near Avignon on 11 September 1095, at Avignon on 13 September, and at Cluny on 25 October. Bishop Bruno accompanied the pope to the Council of Clermont on 18 November 1095, where the First Crusade was inaugurated. After the council, Bruno accompanied the pope to Limoges from 23–31 December. On 31 December, the pope consecrated the new basilica in the monastery of S. Martial, and Bishop Bruno was present. The papal party then proceeded to Charroux before going on to Poitiers on 22 January 1096. Bruno accompanied Urban II to Moyenmoutier, near Tours, where, on 3 March, he was invited to consecrate the capella infirmorum. They were at Tours from 3–25 March, where the pope held a synod; and then to Poitiers again from 29–31 March. Their last two destinations were Nîmes on 12 July, where Pope Urban held a synod, and Saint-Gilles on 20 July. In August 1096, the papal suite began its return to Italy and was in Asti on 9 September; they reached Rome by Christmas.
Pope Urban II died in Rome on 29 July 1099, and was succeeded on 13 August 1099 by Cardinal Rainerius da Bieda, who took the name Paschal II.
In the summer of 1100, Pope Paschal embarked on a tour of southern Italy. Bishop Bruno accompanied him and subscribed a papal privilege for the benefit of Abbot Peter of Cava at Salerno on 30 August 1100.
Bernhard Gigalski argues that it was in the second half of 1102, perhaps between August and December, that Bishop Bruno entered the monastic state at Montecassino. Bruno had accompanied Pope Paschal on his trip to Benevento and had taken part in Paschal's synod there. During the trip, he became seriously ill and decided to resign from his secular pursuits and enter the cloister. He points to the statement in the anonymous life (IV. 5) that it had been five years (quinquennio peracto) after his entry that Bruno was elected abbot on 13 November 1107. Peter the Deacon of Montecassino adds that the people of Segni were put out by Bruno's decision, and complained to Pope Paschal. The pope sent messengers to Bruno, ordering him to "take care of his sheep" and to always be available to the pope for ecclesiastical matters; he also demanded to know why Bruno had retired to a monastery without papal permission. Bruno refused the pope and the people of Segni, which caused the pope to ask Abbot Oderisius of Montecassino to allow Bruno to serve the Roman church for forty days every year.