Carlo Odescalchi, (5 March 1785 – 17 August 1841) was an Italian prince and priest, archbishop of Ferrara, cardinal of the Roman Catholic Church and Vicar of the Diocese of Rome. Close collaborator of popes Pius VII and Gregory XVI, he renounced his titles in order to become a Jesuit in 1838.
He was born in Rome to a family of nobles. His father, Baldassare, was Duke of Sirmio and a prince of the Holy Roman Empire, and his mother was named Valeria Caterina Giustiniani. After being educated at home by his father, Odescalchi studied in Hungary from 1798 to 1800, and he earned doctorates in civil and canon law in 1809. He received the clerical tonsure in 1797 and was eventually ordained to the priesthood on 31 December 1808, celebrating his first Mass on the next day, 1 January. After becoming acquainted with Joseph Pignatelli and following Pope Pius VII's restoration of the Society of Jesus, he planned on entering the Society but failed due to the resistance of his sister Vittoria, who desperately sought to live near her brother. Pius VII himself agreed with Vittoria and promised Carlo that he could enter at a more appropriate time, but after Vittoria's marriage three years later, Pius decided to keep Carlo and appointed him the papal auditor.
Pius VII, following his release from France, sent Odescalchi to Olomouc in 1815 as a papal legate to Antonín Colloredo-Waldsee, and again in 1819 to bestow the cardinalatial red biretta on Rudolf von Habsburg-Lotharingen. From 1815 to 1820, Odescalchi served as auditor of the Sacra Rota Romana for Austria, auditor of the pope, and canon of St. Peter's Basilica.
On 10 March 1823, Pius VII appointed Odescalchi the Archbishop of Ferrara and also created him Cardinal Priest with the title of Santi Apostoli. Odescalchi was consecrated a bishop on the following 25 May by Cardinal Giulio Maria della Somaglia, with Cardinals Giuseppe della Porta Rodiani and Lorenzo Mattei serving as co-consecrators. He served as the papal legate for the opening of the holy door of the Lateran Basilica in the 1825 Holy Year.
Odescalchi resigned as Archbishop of Ferrara on 2 July 1826. He was then named the Prefect of the Congregation of Bishops and Regulars on 5 February 1828.
He was later appointed to two cardinal's posts on 15 April 1833: Cardinal Bishop of Sabina (which he resigned on 30 November 1838, along with the post of Prefect of Bishops and Regulars) and Cardinal Priest of San Lorenzo in Damaso (which he resigned on 19 December 1834).
In 1837, Odescalchi submitted to Pope Gregory XVI his resignation from all his offices to enter the Society of Jesus, but the Pope refused. Appointed Grand Prior of the Sovereign Military Order of Malta in Rome, he again asked the Pope to accept his resignation, which Gregory did this time. After abdicating his cardinalate and episcopate in 1838, Odescalchi finally entered the Jesuit Order on 6 December; he took the habit on the following 8 December and professed his vows on 2 February 1840.
For three years he was much in demand for spiritual retreats to the clergy and rural missions in the Northern part of Italy. He died at the age of 56, at 10:30 a.m., in a Jesuit school in Modena. The correspondence that followed his death suggests that many considered him a saint.
Odescalchi, who ordained Gioacchino Pecci (the future Pope Leo XIII) a priest in 1837, participated in the conclaves of 1823, 1829, and 1830-31. His beatification process was commenced in 1927, and remains open.