Gregorio Leti (1630–1701) was an Italian historian and satirist from Milan, who sometimes published under the pseudonym Abbe Gualdi, L'abbé Gualdi, or Gualdus known for his works about the Catholic Church, especially the papacy. All of his publications were listed on the Index Librorum Prohibitorum.
The nephew of the Bishop of Acquapendente in Umbria, Leti was educated in a Jesuit school, but later became a Protestant. He resided in the court of Louis XIV of France and in 1680 that of Charles II of England, who commissioned him to write a history of England. Leti had access to the library of the Earl of Anglesey, which numbered over 5,000 volumes, as well as that of Bishop Gilbert Burnet. He wrote the first ever proper life of Elizabeth I of England, which includes many romantic embellishments about her youth and her mother, Anne Boleyn. Nevertheless, he may have used documents he found in the English libraries. Leti was also elected a member of the Royal Society.
After the publication of a collection of anecdotes which offended Charles II, Il Teatro Britannico, Leti fled England in 1683 for Amsterdam, where he became the city historiographer in 1685. He died in Amsterdam in 1701.
Leti's biography of Pope Sixtus V has been translated into many languages, and contains an anecdote similar to the infamous "pound of flesh" from William Shakespeare's The Merchant of Venice. The Catholic Encyclopedia calls Leti "mendacious and inexact" and is also critical of works describes as derivative of Leti's "anti-papal histories." Mosheim, a Lutheran church historian, called Leti "inaccurate and unfaithful." According to Thomas Trollope, "his inexactitude as an historian is notorious." Even secular writers have characterized his biography of Sixtus V as "resting on very slight authority." Among his critics, Leti is sometimes referred to as the "Varillas of Italy."
- 1666. Histoire de Donna Olimpia Maldachini.
- 1667. Il Nipotismo di Roma, o vero relatione delle ragioni che muovono i Pontefici all' aggrandimento de' Nipoti ("Papal Nepotism, or the True Relation of the Reasons Which Impel the Popes to make their Nephews Powerful")
- 1668. Il Cardinalissimo di Santa Chiesa.
- 1668 Il Pvttanisno Romano, à Vero, Conclave Generale delle Puttane della Corte From the Collections at the Library of Congress
- 1671. Le visioni politiche sopra gli interessi più reconditi di tutti i principi e repubbliche della Cristianità.
- 1682. La Vita della Regina Elizabetta.
- 1685. L'histoire de la vie du Pape Sixte Cinquième.
- 1685. Il ceremoniale historico e politico, opera utilissima a tutti gli Ambasciatori.
- 1686. Historia Genevrena.
- 1693. Historia overo Vita di Elisabetta, Regina d'Inghilterra.
- 1697. Critique historique, politique, morale, économique, & comique sur les lotteries.
- Krivatsy, Nati. 1982. Bibliography of the Works of Gregorio Leti. Oak Knoll Books New Castle. 8 vols.
- Jewett, Charles Coffin. On the Construction of Catalogues of Libraries, and their Publication by Means of Separate Stereotyped titles. ISBN 1-4021-7529-9. p. 78.
- "Pope Innocent X" in the 1913 Catholic Encyclopedia.
- Ambrosini, Maria Luisa, and Willis, Mary. 1996. The Secret Archives of the Vatican. Barnes & Noble Publishing. ISBN 0-7607-0125-3. p. 138.
- Israel, Jonathan Irvine. 1991. The Anglo-Dutch Moment: Essays on the Glorious Revolution and Its World Impact. Cambridge University Press. ISBN 0-521-54406-8. p. 32.
- Thomas, William John. 1860. Notes and Queries. G. Bell. p. 270.
- Mayer, Thomas Frederick. 1999. A Reluctant Author: Cardinal Pole and His Manuscripts. ISBN 0-87169-894-3. p. 107.
- Chamberlin, Frederick: Elizabeth and Leycester, Dodd, Mead & Co., 1939, pp. 91, 439-440
- Dublin University Magazine. 1852. "Anecdotes of the Stage." in Eclectic Magazine edited by Walter Hilliard Bidwell and John Holmes Agnew. Leavitt, Throw and Co. p. 182.
- Granger, James. 1824. A Biographical History of England. W. Baynes and Son. p. 45.
- Marshall, John. 2006. John Locke, Toleration and Early Enlightenment Culture. Cambridge University Press. ISBN 0-521-65114-X. p. 177.
- Solomon A. 1998. "Shakespeare and the Jews." Renaissance Quarterly. 51, 1.
- "Conclave" in the 1913 Catholic Encyclopedia.
- Mosheim, Johann Lorenz, and Maclainep, Archibald. 1819. An Ecclesiastical History, Ancient and Modern, from the Birth of Christ, to the Beginning of the Eighteenth Century. p. 194.
- Trollope, Thomas Adolphus. 1876. The Papal Conclaves, as They Were and as They are. Chapman and Hall. p. 106.
- Clark, William George, and Wright, William Aldis. 1874. Introduction to The Merchant of Venice. Clarendon Press. p. xx.