The Diocese of Isernia-Venafro () is a Latin Church diocese of the Catholic Church in Molise. It is a suffragan of the archdiocese of Campobasso-Boiano. In 1852 the historic diocese of Isernia was combined with the diocese of Venafro, to form the diocese of Isernia e Venafro. The seat of the present bishop is Isernia Cathedral, while Venafro Cathedral has become a co-cathedral in the new diocese.
History
The epoch of Bishop Benedict of Isernia, and indeed his very existence, is without any documentary evidence at all. It is even claimed that he had predecessors, beginning with Poltinus, who was consecrated a bishop by Saint Peter the Apostle himself. That the existence of the episcopal see in the fifth century is certain is likewise a doubtful proposition; each of the purported bishops has been assigned to other dioceses.<ref>Francesco Lanzoni (1927), Le diocesi d'Italia dalle origini al principio del secolo VII (an. 604), , (Faenza: F. Lega), p. 380: "un s. Benedetto; ma pienamente sconosciuto (cf. A(cta) S(anctorum), mai, I, 500). Seguono nel catalogo Ughelliano un Laurentius (401-17), un Eutodius (465), un Marias (499), un Innocentius (501-2) e un Sebastianus (595) ; ma tutti fuori di luogo. II primo è detto nel documenti { J-L, 318) « episcopus seniensis », probabilmente dell' Illirico; il secondo, il terzo e il quarto spettano a Tifernum (Città di Castello); e l'ultimo a Resinum nella Dalmazia { J-L, 1096; 1853)." Cappelletti XX, pp. 128-129.</ref>
After the Lombard invasions, Isernia was the seat of a countship, founded by the Duke of Benevento. It was destroyed by the Saracens in the ninth century. In 847, the entire city of Isernia was destroyed by an earthquake, with great loss of life, including the bishop.
On 5 May 964, the Lombard princes, Pandulfus and Landulfus, granted the town of Isernia with all its territories to Count Landulfus, at the plea of Bishop Ardericus. The grant recites the boundaries of the territory.
In 1199 it was sacked by Markward von Annweiler, the vicar of the deceased Emperor Henry VI. On 5 December 1456, another great earthquake caused heavy damage and deaths in the area of Isernia. In 1688, both cities were damaged, though apparently the greatest damage was the loss of the church of the Carmelites in Venafro. In 1805, Isernia was struck by a severe earthquake, which ruined the ancient cathedral.
In 1032 the Diocese of Venafro (The town was formerly the site of Roman country residences) was united to Isernia, and in 1230 it was again separated.
On 12 November 1192, the city of Venafro was sacked and burned by the German troops of the Emperor Henry VI, led by Duke Bertold. Bishop Gentile was forced to flee. He sought refuge in Aversa, whose leaders persuaded him to become their bishop. The ecclesiastical leaders in Venafro and in Isernia immediately began to air various grievances against one another, which led to litigation. Numerous citations of the parties to appear before Cardinal Gerardo of S. Adriano, the judge whom Pope Celestine III had appointed, were ignored or put off to a later time. Exasperated, the cardinal authorized the chapter of the Cathedral at Venafro to proceed to elect their own bishop. The Chapter elected Johannes de Abner, but when the pope heard that they had chosen someone who was not even in Holy Orders, he voided the election. Finally, in 1195, he confirmed one R[ - - -] as the new bishop of Venafro. Since the absence of a bishop at Isernia was causing great detriment, Pope Celestine appointed R., the bishop-elect of Venafro, to be the bishop of Isernia as well, ordering the Chapter to obey R. as if they had elected him themselves.
Reorganization of the Kingdom of the Two Sicilies, 1818
Following the extinction of the Napoleonic Kingdom of Italy, the Congress of Vienna authorized the restoration of the Papal States and the Kingdom of The Two Sicilies (Naples). Since the French occupation had seen the abolition of many Church institutions in the Kingdom, as well as the confiscation of much Church property and resources, it was imperative that Pope Pius VII and King Ferdinand IV reach agreement on restoration and restitution.