Capponi was born in 1582, the son of Senator Francesco Capponi and Ludovica Macchiavelli. The Capponi family had extensive links to Italian political circles and to senior members of the Catholic Church. He was educated at the Archgymnasium of Rome where he received a doctorate and became a papal prelate and then treasurer of the Apostolic Chamber. He became a close friend of Cardinal Bonifazio Bevilacqua Aldobrandini.
On 24 November 1608 he was elevated to cardinal and was installed as cardinal-deacon of Sant'Agata dei Goti. In 1614, he was appointed legate in Bologna but fell ill and Cardinal Giulio Savelli was appointed in his place. When he recovered he was appointed cardinal-deacon of Sant'Angelo in Pescheria.
Over the next decade, Capponi was appointed cardinal-priest at a range of churches including San Carlo ai Catinari (1621), San Pietro in Vincoli (1622) and San Lorenzo in Lucina (1629). He also participated in the papal conclave of 1623 which elected Pope Urban VIII.
In 1642 Capponi was appointed co-legate of Bologna, Ferrara and Romandiola along with Pope Urban's cardinal-nephew, Antonio Barberini. When Urban died in 1644, Capponi participated in the papal conclave of 1644 which elected Pope Innocent X.
In 1645 he resigned as archbishop and was appointed prefect of the Sacra Congregatio de Propaganda Fide while Antonio Barberini was in exile in France. In 1649 he was appointed librarian of the Holy Roman Church. He participated in the conclave of 1655.
In 1650, Capponi was visited by French adventurer, François de La Boullaye-Le Gouz. La Boullaye dedicated the first printed edition of his work to the cardinal. The preface includes an illustration of the adventurer presenting the work to Capponi.
Capponi died on 6 April 1659.
- His sister, Clarice Capponi married Vincenzo Magalotti and their daughter married Carlo Barberini, brother of Maffeo Barberini who Capponi would later help elect as Pope Urban VIII
- S. Miranda: Luigi Capponi
- Catholic Hierarchy: Luigi Cardinal Capponi
- G Catholic: Roman Curia – Librarians of the Roman Catholic Church
- Muqarnas – 21 Essays in Honor of J.M. Rogers: An Annual on the Visual Culture of the Islamic World (compiled) by Gülru Necipoğlu, Doris Behrens-Abouseif and Anna Contadini (2005)
|Catholic Church titles|
| Archbishop of Ravenna
Giovanni Garzia Millini
| Cardinal-Priest of San Lorenzo in Lucina
| Librarian of the Holy Roman Church