The first bishop of Carpentras historically documented is Constantinus, who was represented at the Council of Riez in 439, of Orange in 441, and of Vaison in 442. Bishop Julianus was present at a council held at Epaone in 517, and attended local synods in 524, 527 and 529. Siffredus, the patron-saint of Carpentras, succeeded Julianus, and ruled at some time during the period 530-540; he was consecrated bishop by Caesarius of Arles (502-542)
At a national council held at Orléans in 541, Clematius presented himself as Bishop of Carpentras and Venasque, though in the council of 549 he signed only as Bishop of Carpentras. He was also present at the council of Paris in 552.
Later 6th and 7th centuries the bishops called themselves bishops of Venasque, with the exception of Boethius, who at Valence in 584 signed the acts of the council as Bishop of Carpentras. This suggests that, after Carpentras had fallen into ruin, the bishops lived in nearby Venasque.
In 1313, at the beginning of the Avignon Papacy, Pope Clement V took up residence, with the Roman Curia, in Carpentras. The popes resided in the Episcopal Palace in Carpentras. Their comings and goings can be followed by noting the places at which their documents were written and signed.
Following the death of Pope Clement V, and once the mourning for the deceased pope was ended, the Conclave met in the Episcopal Palace at Carpentras. It began around 1 May 1314. The twenty-three cardinals in the Conclave proceeded at a leisurely pace, though without coming to an agreement on the election, until the Feast of S. Mary Magdalen on Monday, 22 July 1314. The Italian cardinals were supporting Guillaume de Mandagot of Lodève, Bishop of Palestrina, who was a Frenchman and a subject of Philip IV of France. The Gascon cardinals, however, who had been appointed by Clement, and were not French subjects, refused to agree. On 22 July rioting broke out among the entourages of various cardinals, and some Gascons (it is claimed) burned down the palace and much of the city. The cardinals scattered, the Italian ones reassembling at Valence and complaining loudly about the Gascons and demanding that the papal Court return to Rome where a proper Conclave could be held. It was not until 28 June 1316, nearly two years later, that the Cardinals reassembled, this time at Lyon, and on 7 August elected Cardinal Jacques Duèse, who became John XXII.
The Comtat Venaissin had been papal property since 1274, a legacy of Alphonse, Count of Poitiers, younger brother of Louis IX of France. The capital, which gave the county its name, had been at Venasque, but in 1320 Pope John XXII transferred the capital to Carpentras.
Carpentras was a suffragan see of Arles from 450 to 1475, when it became a suffragan of Avignon. Its cathedral was the Church of St. Siffrein, of Gothic origins with some Romanesque remains, which was reconstructed in the 15th century and dedicated in 1515.
In accordance with the Concordat of 1801, Carpentras ceased to be a residential diocese later that year, and its territory was incorporated into that of the Diocese of Avignon.
In 1877, the title of bishop of Carpentras, along with those of other ancient sees, was added to that of the archbishops of Avignon and remained so until 2009. Since then Carpentras is listed by the Catholic Church as a titular see. The current titular Bishop of Carpentras is Emmanuel Marie Anne Alain Gobilliard, Auxiliary Bishop Elect of Lyon.
From 1357 to 1371, the Bishop of Carpentras was Jean Roger, the brother of Cardinal Pierre Roger de Beaufort; both were nephews of Pope Clement VI. Under Clement VI and Bishop Jean Roger the walls of Carpentras were constructed, beginning in 1356 and finishing in 1377. As soon as Pierre Roger was elected pope, on 30 December 1370, Bishop Jean Roger was transferred to the more prestigious See of Auch.
Giuliano della Rovere, the future Pope Julius II, was appointed Bishop of Carpentras on 11 October 1471 by his uncle Pope Sixtus IV when he was 27. On 16 December 1471 he was made a cardinal, and on 31 January 1472 he was transferred to the diocese of Lausanne. He therefore had held the diocese of Carpentras for a little over three months, just long enough to collect a pay check. Cardinal Giuliano was not consecrated a bishop until 1481, and should therefore be considered an Administrator. From 21 January 1472, Carpentras was governed by an Administrator, Msgr. Federico di Saluzzo.
Jacopo Sadoleto, the private secretary of Pope Leo X and Pope Clement VII, and one of the great humanists of the sixteenth century, was Bishop of Carpentras from 24 April 1517 until he retired in 1535, resigning the See in favor of his nephew, Paolo, his Coadjutor. As soon as Leo X died in 1521, Jacopo betook himself to his diocese, but he was recalled to Rome by Clement VII shortly after his accession in 1523. Jacopo visited the diocese again in 1524, and returned again in April 1527, just in time to miss the Sack of Rome; he stayed for two years. He was named a cardinal by Pope Paul III on 22 December 1536, with the title of Cardinal Priest of San Callisto and then Santa Balbina.
Joseph-Dominique d'Inguimbert, Bishop of Carpentras from 1735 to 1754, established a scholarly library which Jean-François Delmas, the chief librarian, has called "the oldest of our municipal libraries". Known as the Bibliothèque Inguimbertine and now holding around 140,000 books, it is widely known and is now installed in the former Hôtel-Dieu.
Bishop d'Inguimbert was succeeded on 12 December 1757 by Giuseppe Vignoli of Camerino, Bishop of San Severino (1746-1757). Bishop Vignoli served until 15 July 1776, when he was promoted to the diocese of Forlì.
Bishop Vignoli was succeeded on 16 September 1776 by Giuseppe di Beni, Conte di Gubbio. He had obtained a doctorate in utroque iure from the University of Fano, and was consecrated on 29 September 1776 by Pope Pius VI. He served until 1791, when he was driven out by the French revolutionaries, who forcibly annexed the Comtat Venaissin to the French state. He preferred flight to Italy rather than martyrdom. He was named Administrator of the Diocese of Pesaro on 24 January 1794, and finally resigned the diocese of Carpentras at the request of Pope Pius VI as part of the reconstitution of the Church in France following the Concordat of 1801 with First Consul Napoleon Bonaparte. Bishop Beni died in Pesaro on 12 January 1806.