MONTEFIASCONE, DIOCESE of — In Lazio, in the province of Viterbo; it has an area of 475 sq. km., with a population of 40,000 inhabitants, all Catholics, distributed among 21 parishes, with 50 secular priests and 19 religious, and 5 male and 20 female congregations (Ann. Pont., 1951, p. 277). It has the minor Seminary at M., and the major Seminary, shared with the other dioceses of upper Lazio, at La Quercia near Viterbo.
Continuous discoveries have established that, where M. now stands, there was probably an as-yet-unidentified Etruscan city. Nor has the etymology of M. been determined: it has been derived both from an origin of the highest classical antiquity and from a prosaic allusion to the flasks of its renowned wine. In the Middle Ages, the settlement lay chiefly in the lower part, adjacent to the Via Cassia, around the church of S. Flaviano, whose Romanesque sections date from the 12th century. Its interior, recently subjected to a highly successful restoration by the Superintendency of Monuments of Lazio, consists of two superimposed churches and is of considerable architectural interest.
The oldest notice referring to M. is a privilege granted by Leo IV to Bishop Virbono of Tuscania in the year 852, which Innocent III inserted in one of his letters of 12 October 1207 (PL 215, 1234).
Urban IV (1261–64) had the fortress built as a summer residence; it was also cared for by his papal successors and, during the Avignon exile, served as the seat of the rector of the Patrimony of S. Peter.
Until 1369 M. formed part of the diocese of Bagnoregio, when Urban V, on 30 August of that year, by the bull Cum illius, established the diocese of M. with territory taken from the surrounding dioceses of Castro, Viterbo, Tuscania, and Bagnoregio. However, the first bishop was appointed only seven years later, in 1376, owing to the precarious situation of the Holy See in Italy. He was the Augustinian Pietro Arzensi, who had the misfortune of following the antipope Clement VII and was consequently deposed by Urban VI two years later. In 1436, Eugene IV, separating the city of Corneto from the dioceses of Viterbo and Tuscania, revived the ancient episcopal see of Tarquinia and united it with M. This union lasted until 1854, when Pius IX united Corneto (Tarquinia) with Civitavecchia.
Among the bishops of M., the figure of Cardinal Marcantonio Barbarigo (1687–1706) stands out. He founded the celebrated « Barbarigo » Seminary and promoted the Institute of the Schools of the Pious Teachers. M. is immediately subject to the Holy See. - Vedi tav. XCIII.