The Suburbicarian Diocese of Velletri–Segni is one of the Latin suburbicarian dioceses, Catholic dioceses in Italy close to Rome with a special status and a cardinal bishop, the bishop of Velletri–Segni. Historically, the see of Velletri was combined with the see of Ostia from 1060 to 1914.

The cathedral in the city of Velletri is dedicated to Saint Clement.Kehr, Italia pontificia II, p. 103. Borgia, p. 40.

Segni was a small town, a former Roman colony, sited approximately halfway between Rome and Montecassino. In the 12th century, the diocese possessed only seven castelli, 37 churches, 3 chapels, and 3 cloisters.Bernhard Gigalski (1898), Bruno, Bischof von Segni, Abt von Monte-Cassino (1049-1123): sein Leben und seine Schriften. Kirchengeschichtliche Studien; 3. Bd., 4. Heft (Münster: H. Schöningh, 1898), p. 37. J. P. Migne (ed.), Patrologiae Latinae Collectio Tomus CCI (Paris: Garnier 1903), p. 1158.

Separation of Ostia and Velletri

By the beginning of the 20th century, it had become apparent to the papacy that the suburbicarian bishops had become overburdened with the responsibilities of their curial and diocesan duties. The increase in commerce, in roads and travel, and the migration of people to the city,"hodie, multiplicatis commerciis, expeditioribus itineribus, auctoque proinde numero confluentium hominum, in quotidianum vocantur Fidei morumque discrimen." as well as the increased burden of duties in the papal administration because of the mass and complexity of problems affecting the Church,"Cardinalibus in Urbe negotia adeo sunt multiplicata, ut eorum paene mole obruantur, praesertim ob tot tantasque quibus Ecclesia nunc premitur necessitates... ingravescente praesertim aetate, tempus et vires interdum non sufficiant." made some sort of relief necessary. Pope Pius X therefore issued a document, Apostolicae Romanorum Pontificium, granting the bishops of Ostia, Porto, Palestrina, and Frascati each a suffragan bishop to carry the burden of their pastoral duties in their dioceses. The diocese of Sabina and Velletri are stated to already have had a suffragan bishop, whose powers were in any case henceforth augmented and regulated by Apostolicae Romanorum Pontificium. The appointment of the suffragan bishops was reserved to the Pope. They had full powers inside the diocese, subject to the cardinal bishop's approval, except for the power to ordain or consecrate, or the right to have a throne or display their coat-of-arms. Acta Apostolicae Sedis (Roma, 1910), pp. 277-281.

In 1914, after consulting with the curial cardinals and with their agreement, he issued the document Edita a Nobis. Henceforth, the diocese of Velletri would no longer be permanently united to that of Ostia, so that the suburbicarian dioceses would be: Ostia, Porto and Santa Rufina, Albano, Palestrina, Sabina, Frascati and Velletri. However, by an additional provision a cardinal bishop promoted to the suburbicarian see of Ostia would also retain his previous suburbicarian see.Acta Apostolicae Sedis 6 (Roma 1914), pp. 219-220. As to financial aspects, in future the incomes of the cardinal bishops would be placed in a single fund, administered by the Office of Economic Affairs, to which each cardinal would render an annual account. Each year, after 6,000 Lire had been given to each suffragan bishop, the remaining money collected was to be divided into equal portions, the bishop of Ostia receiving two portions, and each of the other cardinal bishops one portion.

Joining of Velletri and Segni In 1981, the Diocese of Velletri was combined with the Diocese of Segni."Diocese of Segni" Catholic-Hierarchy.org. David M. Cheney. Retrieved February 29, 2016"Diocese of Segni" GCatholic.org. Gabriel Chow. Retrieved February 29, 2016

The Cardinal-Bishop is now the titular bishop of the diocese, while the diocesan bishop administers the diocese.

Reorganization of dioceses In a decree of the Second Vatican Council, it was recommended that dioceses be reorganized to take into account modern developments.Directoriae normae clare a Concilio impertitae de dioecesium recognitione; indicia atque elementa apta ad actionem pastoralem aestimandam ab episcopis suppeditata quibus plurium dioecesium regimen commissum est. A project begun on orders from Pope John XXIII, and continued under his successors, was intended to reduce the number of dioceses in Italy and to rationalize their borders in terms of modern population changes and shortages of clergy. The change was made urgent because of changes made to the Concordat between the Italian State and the Holy See on 18 February 1984, and embodied in a law of 3 June 1985.Diocwesi suburbicaria Velletri-Segni, "Diocesi: Cronotassi"; retrieved: 13 December 2021. The change was approved by Pope John Paul II in an audience of 27 September 1986, and by a decree of the Sacred Congregation of Bishops on 30 September 1986. The diocese of Segni was united to the diocese of Velletri. Its name was to be Dioecesis Veliterna-Signina. The seat of the diocese was to be in Velletri. The former cathedral in Segni was to have the honorary title of co-cathedral, and its Chapter was to be called the Capitulum Concathedralis. There was to be only one episcopal curia, one seminary, one ecclesiastical tribunal; and all the clergy were to be incardinated in the diocese of Velletri-Segni. The territory of the diocese was to be the same as the two dioceses combined.Acta Apostolicae Sedis An. et Vol. LXXIX (Città del Vaticano: Typis Polyglottis Vaticanis 1987), pp. 822-825.

The bishop of Velletri-Segni, Marin Gomiero, was given the authority to carry out the papal decree.

Bishops of Velletri and of Segni

Bishops of Velletri (465–1060)

Adeodatus, 465Lanzoni, p. 146, no. 1. Bonifatius, 487Kehr II, p. 102, no. 1, a document of Pope Gelasius I (492–496), dated to 496. Lanzoni, p. 146, no. 2. Silvinus, 501Lanzoni, p. 146, no. 3, who points out that "Silvinus" is the correct spelling; "Silvanus" was a bishop of Terracina. vacant John I, 592Pope Gregory I granted permission to move the episcopal seat from Arenata because of hostile incursions. Kehr II, p. 102, no. 2. Lanzoni, p. 146, no. 4. Potentinus, 649 Placentinus, 680 John II, 721 Gratiosus (Grosso), 743 Gratian, 761 Citonatus, 761–769 (Bishop of Porto, 769) Gregory I, 769–775 (Bishop of Santa Rufina, 761–769) Theodore, 780 Gregory II 826–853 John III, 853–867 Gaudericus of Velletri, 867–879 John IV, 896–898 Leo I 946–963Schwartz (1913), p. 275. Theobaldo 996–1027 Leo II, 1032–1038 Amato, 1044 Johannes 1050 Benedictus 1057 Johannes Mincius (1058–1060)

United with Ostia in April 1060Hans-Walter Klewitz, Reformpapsttum und Kardinalkolleg, Darmstadt 1957, p. 34

Bishops of Ostia and Velletri (1060–1915) to 1378 Sources for the period 1057–1130: Klewitz (1957), and Hüls (1977). For the period 1130–81: J.M.Brixius.

Peter Damian, 1060–1072Klewitz, p. 115, no. 1. Hüls, pp. 99-100. Gerald of Ostia, 1072–1077Klewitz, p. 115, no. 2. Hüls, pp. 100-101. Odo I de Lagery, 1080–1088 (became Pope Urban II)Klewitz, p. 115, no. 3. Hüls, pp. 102-103. J.N.D. Kelly and M.J. Walsh (2010), Oxford Dictionary of Popes second edition (Oxford: OUP), pp.159-160. Odo II, ca.1088–1102 Leo of Ostia, ca.1106–1115 Lamberto Scannabecchi, 1116–1124 (later Pope Honorius II)Hüls, pp. 106-107. Giovanni of Camaldoli, 1126–1133/35,Giovanni had been Prior of the Benedictine monastery of Camaldoli from 1115. Brixius (1912), pp. 45, no. 22; 134. Hüls, p. 108. Drogo de Champagne, 1136–1138Drogo had been abbot of the Church of S. John in Laon. Brixius, p. 41, no. 9. Alberic, 1138–1148 Guido II de Summa, 1149–1151 Hugo, 1151–1158 Ubaldo Allucingoli, 1159–1181/84 (became Pope Lucius III in 1181) Theobald, 1184–1188 Ottaviano di Paoli, 1189–1206 Ugolino di Conti 1206–1227/31 (became Pope Gregory IX) Rinaldo dei Signori di Ienne, 1231–1254/61 (became Pope Alexander IV in 1254) Hugh of Saint-Cher 1261–1262 Enrico Bartolomei 1262–1271 vacant 1271–1273 Peter VI de Tarentaise, 1273–1276 (later Pope Innocent V, † 1276) vacant 1276–1278 Latino Malabranca Orsini, 1278–1294 Hugh Aycelin, 1294–1297 Leonardo Patrasso, apostolic administrator 1298–1299 Niccolo I Boccasini, 1300–1303 (became Pope Benedict XI) Niccolò Alberti, 1303–1321 Regnaud de la Porte, 1321–1325 vacant 1325–1327 Bertrand du Pouget, 1327–1352 Étienne Aubert, 1352 Pierre Bertrand du Colombier, 1353–1361 Andouin Aubert, 1361–1363 Elie de Saint Yrieux, 1363–1367 Guillaume de la Sudrie, 1367–1373 Pierre d'Estaing, 1373–1377 Bertrand Lagier, O.Min., 1378 (Avignon Obedience)Lagier (Atgerius), a native of Figeac, was named a cardinal in 1371 by Pope Gregory XI. He sided with the obedience of Avignon in the Great Schism. He died on 8 November 1392. Cappelletti I, p. 473. Eubel I, pp. 21, no. 4; 36.

The western schism: Rome vacant 1378–1388 Philippe of Alençon, 1388–1397(Philippe was appointed a cardinal by Urban VI on 18 September 1378. He was promoted Cardinal-bishop of Sabina (1380–1388). He died on 13 August 1397. Cappelletti I, p. 494. Eubel I, pp. 23, no. 16; 36; 38. Angelo Acciaioli, 1397–1408 vacant 1408–1415

The western schism: Avignon (after 1415 restricted to Peñíscola) Bertrand Lagier, 1378–1392 John de Neufchatel, 1392–1398 Leonardo Rossi da Giffoni, 1398–1405 Jean-Allarmet de Brogny, 1405–1408Jean de Brogny was named a cardinal by Pope Clement VII on 15 April 1384. He was promoted to the see of Ostia-Velletri on 13 June 1405. He died on 16 February 1426. Cappelletti I, p. 474. Eubel I, pp. 28, no. 26; 36. vacant 1408–1423 Julian Lobera y Valtierra, 1423–1429 (restricted to Peñíscola)

The western schism: Pisa Jean-Allarmet de Brogny, 1409–1415In 1408, most of the cardinals of both Obediences renounced their allegiances, and participated in summoning the Council of Pisa. The Council deposed Benedict XIII and Gregory XII; the twenty-four cardinals then held a conclave and elected Pope Alexander V, who legitimized all of the cardinals of both Obediences. Jean-Allarmet de Brogny, 1415–1426Pope John XXIII was deposed by the Council of Constance on 29 May 1415. Gregory XII resigned his claims on 4 July 1415, and was appointed Cardinal Bishop of Porto and Legate of the Marches by the Council. On 11 November 1417, a special and unique conclave, presided over by Jean Allarmet de Brogny, elected Cardinal Oddone as Pope Martin V.

Since the end of the schism

Antonio Correr, 1431–1445Correr was named a cardinal in 1409 by Pope Gregory XII. He was previously Cardinal-bishop of Porto (1409/17–1431). He died on 19 January 1445. Eubel, Hierarchia catholica II, pp. 4, no. 5; 60. Juan de Cervantes, 1447–1453Cervantes had been Cardinal priest of S. Pietro in Vincoli (1426–1447). He died in Spain on 25 November 1453. Eubel I, pp. 34, no. 8; 36; 45. Giorgio Fieschi, 1455–1461Fieschi was formerly Cardinal-bishop of Palestrina 1449–1455. Guillaume d'Estouteville, 1461–1483Named a cardinal by Pope Eugenius IV in 1439, Estouteville was archbishop of Rouen (1453–1483); he had been Cardinal-bishop of Porto (1455–1461). He died on 22 January 1483. Eubel II, pp. 8, no. 18; 60; 225 with note 2. Giuliano della Rovere, 1483–1503,Kelly and Walsh (2010), Oxford Dictionary of Popes, pp. 258-259. Salvador Miranda, The Cardinals of the Holy Roman Church-Biographical Dictionary "Della Rovere, Giuliano"; retrieved: 2 December 2021. (became Pope Julius II) Oliviero Carafa, 1503–1511Carafa had previously been Cardinal-bishop of Albano (1476–1483), and Cardinal Bishop of Sabina (1483–1503). He died in Rome on 20 January 1511. Eubel III, pp. 3, no. 2; 56; 58. Raffaele Riario Sansoni, 1511–1521Riario was a nephew of Pope Sixtus IV. He had previously been Cardinal-bishop of Albano (1503–1507), of Sabina (1507–1508), and of Porto (1508–1511). He died on 9 July 1521. Eubel III, pp. 3, no. 6; 55-58.