The Diocese of Montalto (Latin: Dioecesis Montis Alti) was a Latin Church ecclesiastical territory or diocese of the Catholic Church located in the town of Montalto delle Marche in the Province of Ascoli Piceno in the Italian region of Marche. The diocese was erected in 1586 by Pope Sixtus V (Felice Peretti di Montalto), a native of the town. The diocese was suppressed in 1986, and its territory was assigned to a new entity, called the Diocese of San Benedetto del Tronto–Ripatransone–Montalto."Diocese of Montalto (delle Marche)" Catholic-Hierarchy.org. David M. Cheney. Retrieved May 17, 2017"Diocese of Montalto " GCatholic.org. Gabriel Chow. Retrieved May 17, 2017

Ecclesiastical history On 24 November 1586, the Diocese of Montalto was established from territory split from the Diocese of Fermo.Cappelletti, pp. 721-724.

In a papal bull of 18 December 1924, Pope Pius XI united the Diocese of Ripatransone with the diocese of Montalto ad personam episcopi. He appointed Luigi Ferri as Bishop of Ripatransone with Montalto, and ordered a change in the title of the bishop to Episcopus Montis alti et Ripanus."Cathedrali Ecclesiae Ripanae, cum Ecclesia Montis alti in personam unitae, R. P. D. Aloisium Ferri, Episcopum Montis alti, qui posthac Episcopus Montis alti et Ripanus appellabitur." Acta Apostolicae Sedis 16 (1924), p. 498. Diocesi di San Benedetto del Tronto-Ripatransone-Montalto, "Storia della diocesi"; retrieved: 1 April 2020. In 1980, the diocese of Montalto had a population of only 31,500 persons.Annuario pontificio 1981.

Restructuring The Second Vatican Council (1962–1965), in order to ensure that all Catholics received proper spiritual attention, decreed the reorganization of the diocesan structure of Italy and the consolidation of small and struggling dioceses. It also recommended the abolition of anomalous units such as exempt territorial prelatures.In its decree Christus Dominus, section 22, it stated: "Concerning diocesan boundaries, therefore, this sacred synod decrees that, to the extent required by the good of souls, a fitting revision of diocesan boundaries be undertaken prudently and as soon as possible. This can be done by dividing dismembering or uniting them, or by changing their boundaries, or by determining a better place for the episcopal see or, finally, especially in the case of dioceses having larger cities, by providing them with a new internal organization.... At the same time the natural population units of people, together with the civil jurisdictions and social institutions that compose their organic structure, should be preserved as far as possible as units. For this reason, obviously, the territory of each diocese should be continuous." These considerations applied to Montalto and to Ripatransone as the population migrated in the post-war period to jobs on the coast at San Benedetto.

On 18 February 1984, the Vatican and the Italian State signed a new and revised concordat. Based on the revisions, a set of Normae was issued on 15 November 1984, which was accompanied in the next year, on 3 June 1985, by enabling legislation. According to the agreement, the practice of having one bishop govern two separate dioceses at the same time, aeque personaliter, was abolished. Instead, the Vatican continued consultations which had begun under Pope John XXIII for the merging of small dioceses, especially those with personnel and financial problems, into one combined diocese. On 30 September 1986, Pope John Paul II ordered that the dioceses of Ripatransone and Montalto be merged into one diocese with one bishop, with the Latin title Dioecesis Sancti Benedicti ad Truentum-Ripana-Montis Alti. The seat of the diocese was to be in San Benedetto del Tronto, and the church of S. Maria della Marina was to serve as the cathedral of the merged dioceses. The cathedrals in Ripatransone and Montalto were to become co-cathedrals, and the cathedral Chapters were each to be a Capitulum Concathedralis. There was to be only one diocesan Tribunal, in San Benedetto del Tronto, and likewise one seminary, one College of Consultors, and one Priests' Council. The territory of the new diocese was to include the territory of the former dioceses of Montalto and Ripatransone.Acta Apostolicae Sedis 79 (Città del Vaticano 1987), pp. 747-749.

The town is the site of the cathedral of Montalto delle Marche, dedicated to the taking up of the body of the Virgin Mary into heaven (Assumption).

Bishops of Montalto Paolo Emilio Giovannini (1586–1606)A native of the village of Porchia in the Marche, Giovannini held the degree of Doctor in utroque iure, and was Provost of the parish church of San Lorenzo di Gatteo. He was sent as a junior member on papal legations to France (he was there in May 1555), to Spain, and to Poland (1563–1565). He became a Canon of the cathedral of Ravenna, and served as Vicar General of the diocese of Cesena. He was named Bishop of Montalto by Pope Sixtus V on 26 November 1586. He died on 6 August 1606. Ughelli II, p. 751. Cappelletti III, p. 724. Eubel, Hierarchia catholica III, p. 248 with note 3. Tiberio Mandosi (1606–1607)Mandosi, of a noble family of Amerino, was born in Rome. He held the degree of Doctor in utroque iure, and was a Canon of the Vatican Basilica. He received his appointment as Bishop of Montalto on 11 December 1606 from Pope Paul V, on the recommendation of Cardinal Alessandro Peretti, his patron. He died in Rome on 3 November 1607 in his 53rd year, after less than a year as bishop. Ughelli II, p. 752. Gauchat, Hierarchia catholica IV, p. 246 with note 2. Paolo Orsini, O.P. (1608–1640)Orsini was a Roman noble, belonging to the Bracciano branch of the Orsini family; his father was Giordano Orsini, son of Paolo, and Laura Carducci, a patrician of Florence. His eldest brother, Ottavio, was Bishop of Venafro and then of Segni (1632–1640); his brother Sforza Orsini was a Knight of the Order of Malta. Six of his sisters were nuns. Paolo was a monk at Santa Maria sopra Minerva in Rome. He was named Bishop of Montalto on 14 July 1608. He died on 12 April 1640. Ughelli II, p. 753. Gauchat, p. 246 with note 3. Orazio Giustiniani, C.O. (1640–1645)A native of Genoa of a family originally from Chios in the Aegean, Giustiniani was appointed Bishop of Montalto by Pope Urban VIII on 13 February 1640. He was named Bishop of Nocera Umbra (Italy) on 16 January 1645. He served there until 16 February 1646, when he was appointed Cardinal-Priest of S. Onofrio (1645–1649) by Pope Innocent X. He served as Librarian of Vatican Apostolic Library from 25 September 1646 to his death on 25 July 1649. He was also Major Penitentiary of Sacred Apostolic Penitentiary (1647–1649). Ughelli II, p. 753-754. Gauchat, pp. 28, no. 8, with notes 4 and 5; 246 with note 4; 262 with note 4. Girolamo Codebò (1645–1661)Count Girolamo Codebò belonged to a noble family of Modena. He was Provost of the collegiate church of Carpi, and Archpriest of the cathedral of Carpi (1625–1629). He was a Referendary of the Two Signatures (judge) in the Roman Curia, and served successively as papal Governor of the cities of Tivoli (1622, 1624), Terni (1634), Rieti (1636), Benevento (1636), Ascoli Piceno (1639), Spoleto (1640–1643), and Camerino (1643). Codebò was appointed Bishop of Montalto on 10 February 1645 by Pope Innocent X. He was transferred to the diocese of Reggio Emilia on 24 January 1661. He died on 3 October 1661. Ughelli II, p. 754. Cappelletti, p. 725. Gauchat, p. 246 with note 5; 294 with note 6. Cesare Cancellotti, C.O. (1662–1673)Cancellotti was a native of San Severino, born in 1604. He held the degree of Doctor in utroque iure, and had been Archdeacon of the cathedral of San Severino, and Vicar General of the bishop. He was named Bishop of Bisceglie (April 1658 – 16 June 1662) by Pope Alexander VII. He was transferred to the diocese of Montalto by Alexander VII on 16 June 1662. He died on 27 June 1673. Cappelletti, p. 725. Gauchat, pp. 246 with note 6; 369 with note 7. Ascanio Paganelli (1673–1710)Born in Camerino, Paganelli held the degree of Doctor in utroque iure, and was a privy chamberlain of Pope Clement X. He was appointed Bishop of Montalto on 11 September 1673, by Pope Clement X. He died in April 1710, according to Ughelli and Ritzler-Sefrin. Others report 30 June 1710. Ughelli II, p. 754. Ritzler-Sefrin, Hierarchia catholica V, p. 273 with note 3. Lucantonio Accoramboni (1711–1735)Accoramboni was born in Gubbio in 1666. He held the degree of Doctor in utroque iure from the University of Macerata (1695). He was Vicar General of Città della Pieve, and Vicar Apostolic of Sorana and of Terracina. He was then Vicar General of the suburbicarian diocese of Albano. He was named Bishop of Montalto on 11 May 1711. He died on 1 September 1735. Ughelli II, p. 754. Ritzler-Sefrin, Hierarchia catholica V, p. 273 with note 4. Pietro Bonaventura Savini (1735–1748 retired)Savini was named Bishop of Montalto on 26 September 1735. On retirement on 26 September 1748, Savini was granted the courtesy title of Titular Archbishop of Sebastia. Leonardo Cecconi (1748–1760)Cecconi was born in Palestrina in 1691. He was named Bishop of Montalto on 26 September 1748. He died on 24 March 1760. He was the author of a history of Palestrina: Ritzler-Sefrin, Hierarchia catholica VI, p. 294 with note 3. Giuseppe Maria Centini (1760–1770)Centini was born in Ascoli Piceno in 1700. He held the degree of Doctor in utroque iure from the University of Macerata (1731). He served as civil governor of various cities in the Papal States: Reate, Benevento, Città di Castello, Aesina, and Montalto, and was Commissary Apostolic in the city of Naples. In Rome he was appointed Referendary of the Tribunal of the Two Signatures. He was approved as Bishop of Montalto by Pope Clement XIII on 24 September 1760. He died in Montalto on 15 May 1770. Ritzler-Sefrin, Hierarchia catholica VI, p. 294 with note 4. Francesco Antonio Marucci (1770–1798)Marucci was named Bishop of Montalto on 6 August 1770, by Pope Clement XIV. On 10 December 1781, Marucci was appointed by Pope Pius VI to the post of Titular Latin Patriarch of Constantinople. He died on 19 July 1798. Francesco Saverio Castiglioni (1800–1816)Castiglioni was named Bishop of Montalto on 11 August 1800 by Pope Pius VII. He was transferred to the diocese of Cesena on 8 March 1816, by Pope Pius VII. He held the diocese until 4 August 1821. He was appointed Cardinal-Priest of S. Maria in Traspontina on April 29, 1816, and on August 4, 1821 Major Penitentiary. He was promoted Cardinal-Bishop of Suburbicarian Diocese of Frascati on 13 August 1821, and on 14 November 1821 was named Prefect of the Roman Sacred Congregation of the Index. He was elected Pope Pius VIII on 31 March 1829, and died on 30 November 1830. Pietro Paolo Mazzichi (1817–1823)Mazzichi had been Vicar General of the diocese of Assisi. He was appointed Bishop of Montalto on 14 April 1817. He died on 9 May 1823. Cappelletti III, p. 726. Ritzler-Sefrin, Hierarchia catholica VII, p. 270. Filippo Ambrosi (1823–1825)Ambrosi was a native of Ascoli Piceno, born in 1755. He was a Canon of the cathedral of Ascoli, and taught Canon Law at the seminary of Ascoli. He served as Vicar General of the diocese. He was offered the diocese of Tivoli by Pope Pius VII (1800–1823), but he declined. He was appointed Bishop of Montalto on 17 November 1823 by Pope Leo XII. He died on 28 May 1825, at the age of seventy. Studia picena (Fano: Pontificio seminario marchigiano "Pio XI", 1940), p. 100. Ritzler-Sefrin VII, p. 270.