(b. 1599, Bissone, d. 1667, Roma)
Italian architect of Swiss origin (original name Francesco Castelli). He was the son and student of Giovanni Domenico Castelli, a builder in the service of the Visconti family of Milan. He took his mother's maiden name of Borromini to distinguish himself from numerous Castelli relatives.
Borromini was introduced to the craft specialities of architecture when his father sent him to Milan (1608 or 1614) to learn stonecutting. After several years training in the skills and technology of both architecture and sculpture, he collected a debt owed to his father and, without informing his parents, fled to Rome in 1619.
In Rome, he became a draftsman and stonemason in the office of his kinsman, Carlo Maderno, who had established himself as the major practicing architect in Rome, the official architect to St. Peter's. When Maderno died in 1629, Borromini joined the workshop of Bernini, and under Bernini he gained more experience as a draftsman and designer. In 1634 he began work as an independent architect with his reconstruction of the monastery and church of St. Carlo Borromeo. His most extravagant effort was the church of San Carlo alle Quattro Fontane, a good example of the fully developed Baroque style in Rome. In the church and part of the College of Propaganda, Borromini's fancies are wildest; the cupola and campanile of Sant'Andrea delle Fratte are in better taste. The great nave of San Giovanni Laterano was modernized, as it now stands, by Borromini. He contributed to the construction of Sant'Agnese in the Piazza Navona, originally designed by Girolamo and Carlo Rainaldi.
Borromini was honoured by the Pope in 1652 and made a knight of Christ. In his career, although his work provoked dispute and discussion, he became successful and an important figure in Baroque architecture. Despite this, it seems that Borromini was troubled, described as 'neurotic' and perfectionist, and maintained a bitterness towards Bernini's greater fame. In the last few days of his life in 1667, he was extremely agitated and is thought to have destroyed many of his drawings. In August 1667 he committed suicide.
He left a significant work unfinished - a collection of engravings of his buildings begun shortly before his death. These were published some 60 years later as Opus architectonicum equitis Francisci Boromini.
Borromini secured a reputation throughout Europe with his striking design for the small church, San Carlo alle Quattro Fontane in Rome. He differed from Gian Lorenzo Bernini and other contemporaries in basing his designs on geometric figures (modules) rather than on the proportions of the human body.