The Diocese of Duvno (; ) was a Latin rite particular church of the Catholic Church that was established in the 14th century with a seat in present-day Tomislavgrad in Bosnia and Herzegovina. It was a suffragan diocese of the Archdiocese of Split, and during the 17th century of the Archdiocese of Dubrovnik. The diocese consisted of four parishes: Roško Polje, Duvno, Posušje and Rama.
The diocese was established under the patronage of the Šubić family. The seat of the diocese was in the former fortress of Rog, located in present-day Roško Polje near Tomislavgrad, and the cathedral church was the Church of St. John the Baptist. Due to the Ottoman incursions in the diocese from the 1460s to the final conquest of the diocese in the 1480s, the bishops of Duvno resided on the territory of the Archdiocese of Split. Vid of Hvar, who ruled the diocese until 1507, was the last bishop active in the diocese until 1551. Until that time, the diocese was nominally held by titular bishops, followed by a line of the so-called missionary bishops, the first of whom was Daniel Vocatius. The missionary bishops resided in the Ottoman territory, in the Franciscan friary in Rama, which belonged to the diocese of Duvno, but after its destruction by the Ottomans in the late 17th century, they continued to administer the diocese from the Archdiocese of Split, while they were helped by the Illyrian priests and the Bosnian Franciscans who lived under the Ottomans. From 1610 to 1645, the diocese was again ruled only nominally by titular bishops, and after that, by the missionary bishops and the bishops of the neighbouring Makarska. From 1800, the title of the bishop of Duno was only titular until 1881, when the diocese was incorporated into the newly established Diocese of Mostar-Duvno after Austria-Hungary occupied the Ottoman-held Bosnia and Herzegovina.
History
Background
In the 14th century, when the Diocese of Duvno was established, the Archbishop of Split had a right to establish dioceses in his metropolitan area and appoint and consecrate the bishops. The exact year of the establishment of the Diocese of Duvno remains unknown. It is not mentioned before the rule of Paul I Šubić of Bribir, and it was most probably established by the Archbishop of Split Petar, O.F.M., who served as the archbishop from 1297 to 1324. The establishment of the Diocese of Duvno, as well as the dioceses Šibenik and Makarska was initiated for the political goals of the Šubić family, the dukes of Bribir. Namely, in this way, they would secure support among the clergy.
On the verge of the 13th to 14th century, the sons of Paul Šubić – Mladen, George and Paul, after securing the territory of the eastern Adriatic hinterland, adopted the title of a "Duke of Tropolje, Livno and Cetina". They intended to extend their territories further east towards the hinterland and establish the highest church organisation there.
At the time, the circumstances within the Papacy allowed the Šubić's to implement their church policy. The Papacy at the time, faced complex issues, including the dispute with Philip IV of France over the taxation of clergy and expropriation of the church's property and especially the property previously owned by the Knights Templar. This resulted in moving the papal seat to Avignon. The Avignon popes used the church institutions mainly to collect taxes to build their new residence in Avignon. As the Šubić's were able to issue their own currency, they were wealthy and good taxpayers, so they were allowed to pursue their church policies.
The rival to the Šubić family were the Kotromanićs who ruled the Banate of Bosnia. For example, Stephen II Kotromanić, although himself a Latin Catholic, supported the heterodox Bosnian Church, which in return, supported the claims of the Kotromanić family. The Bosnian Church, protected by the Kotromanić family, managed to expand outside of its Bosnian core to Zachlumia, Tropolje and the area between Neretva and Cetina. Thus, the Šubić's were seen as the fighters for the orthodoxy against the heterodox Bosnian Church. Thus, Pope John XXII calls Mladen II Šubić to remove "the enemies of the Christ's Cross" from Bosnia. The Šubić's mission to appropriate the members of the Bosnian Church to the Catholic Church gained them a favour among the Bosnian Franciscan missionaries. They constructed Franciscan friaries and appointed Franciscans as bishops in the dioceses under their control.