Francesco Faà di Bruno (29 March 1825–27 March 1888) was an Italian mathematician and priest, born at Alessandria. He was of noble birth, and held, at one time, the rank of captain-of-staff in the Sardinian Army. He is the eponym of Faà di Bruno's formula. In 1988 he was beatified by Pope John Paul II.
Coming to Paris, he resigned his commission, studied under Augustin Cauchy, and Urbain Le Verrier, who shared in the discovery of the planet Neptune, and he became intimate with Abbé Moigno and Charles Hermite. On his return to Turin, he was ordained, but the remainder of his life was spent as Professor of Mathematics at the University. In recognition of his achievements as a mathematician, the degree of Doctor of Science was conferred on him by the Universities of Paris and Turin.
In addition to some ascetical writings, the composition of some sacred melodies, and the invention of some scientific apparatus, Faà di Bruno made numerous and important contributions to mathematics. Today, he is best known for Faà di Bruno's formula on derivatives of composite functions, although his role in developing this formula is controversial.
He was the author of about forty original articles published in the "Journal de Mathématiques" (edited by Joseph Liouville), Crelle's Journal, "American Journal of Mathematics" (Johns Hopkins University), "Annali di Tortolini", "Les Mondes", "Comptes rendus de l'Académie des sciences", etc.; the first half of an exhaustive treatise on the theory and applications of elliptic functions which he planned to complete in three volumes; "Théorie générale de l'élimination" (Paris, 1859); "Calcolo degli errori" (Turin, 1867), translated into French under the title of "Traité élémentaire du calcul des erreurs" (Paris, 1869); and most important of all, "Théorie des formes binaires" (Paris, 1876), translated into German (Leipzig, 1881). For a list of the memoirs of Faà di Bruno, see the "Catalogue of Scientific Papers of the Royal Society: (London, 1868, 1877, 1891), t. II, vii, and ix.
* Faà di Bruno, for other members of the family.
1. ^ The twelfth child of Luigi Faà, marchese of Bruno, conte of Carentino, signore of Fontanile and patrizio of Alessandria, and of the noblewoman Carolina Sappa de’ Milanesi. See 
* O'Connor, John J.; Robertson, Edmund F., "Francesco Faà di Bruno", MacTutor History of Mathematics archive, University of St Andrews, http://www-history.mcs.st-andrews.ac.uk/Biographies/Faa_di_Bruno.html .
This article incorporates text from the Catholic Encyclopedia of 1913, a publication now in the public domain.