The Diocese of Reggio Emilia–Guastalla () is a Latin diocese of the Catholic Church in Emilia-Romagna, Italy. It has existed in its current form since 1986. In that year the historical Diocese of Reggio Emilia was united with the Diocese of Guastalla. The diocese is a suffragan of the Archdiocese of Modena–Nonantola.

Originally the diocese was part of the ecclesiastical province of Milan, then it was suffragan to the Archbishop of Ravenna.Kehr, p. 365. Because of the schism of the Antipope Clement III, Pope Paschal II released the dioceses of Emilia, including Reggio, from obedience to the church of Ravenna, and made them directly subject to the Holy See (Rome), but twelve years later Pope Gelasius II restored the previous status.Kehr, p. 299. Bishop Enrico de Casalorci attended the provincial synod of Ravenna in 1310–1311, and sent a procurator to the synod of 1314. Saccani, pp. 85-86. In 1582 the diocese of Bologna was raised to the status of a metropolitan archbishopric. Reggio was made a suffragan of the archdiocese of Bologna, by Pope Gregory XIII in the bull Universi orbis of 10 December 1582. Modena was raised to the status of an archdiocese and its bishop to the status of a Metropolitan Archbishop by Pope Pius IX in his bull of 22 August 1855, entitled Vel ab antiquis. Reggio became one of its suffragans.Cappelletti, pp. 298-308.

History A local legend makes the first bishop of Reggio Saint Protasius, a disciple of Saint Apollinaris, a first-century disciple of Saint Peter himself. Admitting his existence, also five or six historical bishops, predecessors of Faventius in 451,The existence of Protasius and five other of the earliest bishops is not accepted by modern scholars. Gams, p. 760 column 2. Lanzoni, pp. 794-795. Kehr, p. 365: Reginensium rerum scriptores primum Reginae civitatis antistitem Protasium, b. Apollinaris discipulum, celebrant, sed Protasii ceterorumque qui ei successerunt episcoporum nomina fabulosa sunt. it would seem that the episcopal see dates from the first half of the 4th century. Bishop Prosper was a successor of Faventius; he died between 461 and 467.

Bishop Teuzo (978–1030) was named a Missus of the Holy Roman Empire by the Empire by the Emperor Conrad II (1027–1039). This brought with it the title of Prince, and the bishops of Reggio continued to enjoy the privilege and title until the end of the 14th century.Saccani, p. 52.

In the Capitulary of Quierzy, Reggio was included among the towns which Pepin had in mind for the Donation of Pepin, but it came into possession of the Papal States only later, and for a short time.Compare the narrative in the Liber pontificum (a partisan papal statement), which makes no mention of Reggio, unless perhaps it is included in the 'entire duchy of Ferrara'. After the death of Countess Matilda (1115) the popes claimed the town as a part of her inheritance, while the emperors claimed the same as a fief of the Holy Roman Empire.

On 21 April 1141, the metropolitan Archbishop of Ravenna, Gualterius, was obliged to hold a synod at Reggio, for the purpose of composing the differences which existed between the people and their leaders, as well as disputes among the leading clergy of the diocese. The synod was attended by Bishop Alberio of Reggio, as well as by four other bishops. The Archdeacon of Reggio had issues with the canons of the cathedral and with the brothers of S. Prospero as well, over various chapels and pieces of property.J. D. Mansi (ed.), Sacrorum Conciliorum nova et amplissima collectio, editio novissima, Tomus XXI (Venice: A. Zatta 1776), pp. 569-572. C. J. Hefele, Histoire des Conciles Tome VII (Paris: Adrien Le Clere 1872), p. 288.

Bishop Nicolò Maltraversi According to the Cronica of Fra Salimbene of Parma, Nicolò was named bishop in 1211, with the approval of both the Emperor Otto IV and Pope Innocent III. But on 8 April 1213, he is still called bishop-elect. Only on 25 September 1213 does he have the full title of Bishop of Reggio.Cappelletti, p. 377, citing the words of Fra Salimbene in full. In Piacenza he attempted to broker a peace between the Ghibelline Sessi and the Guelph Roberti-Fogliani.Panciroli, I, pp. 166-167; 170-171; 175-177; 181. Saccani, p. 79. In 1221 he helped Cardinal Ugolino (later Pope Gregory IX) preach the crusade in northern Italy. In 1224, he was papal mediator in peace talks between Bologna and Mantua. In May and June 1230, Bishop Nicolò dei Maltraversi (1211–1243) accompanied an embassy of the Emperor Frederick II to Pope Gregory IX, in the hope of bringing peace between Empire and Church. On 1 July 1230 he was present in the major church of San Germano to witness the papal reconciliation with the Emperor. In 1233, he was granted the right to issue coinage by Frederick II.Panciroli. p. 173. In April 1242, the Emperor Frederick wrote a letter to Bishop Maltraversi, expressing his joy at the bishop's success in bringing his nephews and other relatives (consanguineos et nepotes tuos) back to the imperial side (the Ghibellines) and loyalty to the Emperor; he urged Nicolò to return to him as soon as possible, to assist in some difficult and useful matters. Panciroli, Storia della città di Reggio I, pp. 180-182.

When Bishop Nicolò died in 1243, probably in August, the new pope, Innocent IV (Sinibaldo Fieschi of Genoa), immediately issued a decree on 24 August, reserving for himself the right to appoint (provisio) a new bishop of Reggio.Eubel, I, p. 417, note 1. Nonetheless, on 2 September 1243, he wrote to the Bishop of Modena and to his own nephew, the Archdeacon of Parma, that they should lift the sentences of excommunication which had been pronounced against the Canons of Reggio, and order the Canons to elect a bishop within twenty days; otherwise, the Bishop of Modena should choose a suitable candidate as bishop. When the Canons proceeded to an election, two candidates were produced: the Ghibellines supported the Provost of S. Prospero, Guicciolo Albriconi; the Guelphs supported Guglielmo Fogliano, a canon of the cathedral and a nephew of Pope Innocent. According to Fra Salimbene, there were extensive disturbances (magna discordia) in the city in September.Cappelletti, p. 379-380. After an investigation of the canonical validity of the election,On 2 October, Innocent ordered the Archbishop of Ravenna to confirm one of the parties; on 20 October, Innocent wrote that the election was to be submitted to the Holy See, since Gucciolo was excommunicated and the election was canonically irregular; on 1 December, he ordered the Bishop of Modena to cite the two electi to appear at the Papal Court; on 6 February 1244, the Pope announced that the election had been quashed, and that a new election was forbidden. Eubel, I, p. 417, note 1. the Pope pronounced his nephew to be the new bishop. Since the agents of the Emperor Frederick's son Enzo had possession of the episcopal palace, Bishop-elect Fogliano was forced into exile.Saccani, pp. 79-80. He did not gain possession of the diocese until 1252, and was still not consecrated bishop by 23 May 1255, when he received an extension on the time-limit.Saccani, p. 80, note 4. Eubel, I, p. 417, note 1.

The election of 1301–1302 Bishop Guglielmo of Bobbio died at Bobbio on 3 September 1301. The Chapter of the cathedral of Reggio met, and at the request of Azzo d'Este, Lord of Reggio, they unanimously elected Fra Giovannino dei Melonelli, O.Min. The Minister General of the Franciscans, however, refused to sanction the election, and Pope Boniface VIII therefore quashed the election. The Pope then nominated Matteo Visconti, a Canon of the cathedral of Milan, who refused the election. Finally, on 3 April, in a public consistory, the Pope proposed the name of Enrico de Casalorci, who was a Canon of the cathedral of Cremona. His appointment was published at the Lateran on 30 April, and he was consecrated at Anagni by Cardinal Matteo di Aquasparta, Bishop of Porto, on 22 July 1302. His formal entry into his diocese took place on 17 August.Saccani, p. 85. Eubel, p. 417, with note 3.

Bishop Serafino Tavacci, O.Min. (1379–1387) was the first bishop of Reggio to enjoy the title Prince.Saccani, p. 98.

Imperial Reggio

Reggio accepted the vicars of Emperor Henry VII and Louis the Bavarian, and was subject to the pope under Cardinal Bertrand du Poyet (1322). Later (1331), John of Bohemia, who recognized the suzerainty of the pope over Reggio as well as over Parma and Modena, was made lord of the city, but sold it to the Fogliani, from whom it passed to the Gonzaga of Mantua (1335), who sold it to Galeazzo II Visconti of Milan. In 1409 it returned again to the House of Este of the line of Modena, until 1859. The popes, however, always claimed to be its suzerains. After the Ferrara War, Reggio spontaneously submitted to Pope Julius II (1512–15). By the Peace of Barcelona (1529), Emperor Charles V bound himself to give back Reggio to the popes, but he did not do so.

Plague Reggio Emilia was stricken particularly hard by the bubonic plague from 1630 to 1632, the result of German troop movements in the war between the French and the Empire. The Church began its campaign against the plague on 18 April 1630, with a procession ordered by the bishop and magistrates, which featured the carrying of the right foot of Mary Magdalene, the head of Saint Maurizio, arms of S. Reparata and S. Catherine, and the remains of S. Apollonia, S. Abondonio, and S. Prospero.Fano, p. 35. An inscription at Guastalla states that 2,104 persons had died in one parish alone.Fano, p. 14, note 2. At Gualtieri, by 20 March 1631, 463 out of a population of 1380 had died.Fano, p. 48. Inside the city of Reggio, 3617 persons died of the plague, and outside the city an additional 2,130.Fano, p. 15.

Bishop Augusto Bellincini (1675–1700) was responsible for the introduction of the Priests of the Mission (C.M.) to the diocese of Reggio (1681). He also found quarters for the Discalced Carmelites (O.C.D.) in 1685, and introduced the Discalced Carmelite nuns to the diocese (1689). He also welcomed the Minims of S. Francesco di Paola in 1696.Saccani, p. 140.

Cathedral and Chapter On 13 June 1200, Pope Innocent III, in the bull Cum a nobis, at the request of the chapter of the cathedral, fixed the maximum number of Canons which the Chapter could have at sixteen. This was necessary, the bull states, because numbers of relatives and hangers-on who obtained canonries were appropriating the property belonging to the Chapter.Cappelletti, pp. 375-377.

Bishop Nicolò dei Maltraversi (1211–1243) suppressed the office of Provost of the Cathedral in 1212.Saccani, p. 74.

In 1674, the Cathedral Chapter consisted of three dignities and fifteen Canons.Ritzler-Sefrin, V, p. 331, note 1. The dignities were: the Archpriest, the Archdeacon, and the Majuscola (Magister Scholae). In addition, in accordance with the decrees of the Council of Trent, one Canon was designated the Theologus, and another the Penitentiary. In 1857, there were those five, plus eight other Canons.Almanacco della R. corte e degli stati Estensi (Modena: Eredi Soliani 1857), p. 385.

Synods Bishop Benedetto Manzoli held a diocesan synod in Reggio in 1581. Synods were held by Bishop Claudio Rangoni (1592–1621) on 20 June 1595, and on 17 July 1597.Constitutiones et decreta synodalia diversis temporibus ab illustriss et reverendiss. d.d. Co. Claudio Ragono, episcopo Regii et principe, condita, et in unum hac secunda editione congesta (Reggio: Flaminio et Flavio Bartholi 1614).