Girolamo Alessandro Frescobaldi (Italian: [dʒiˌɾɔːlamo fɾeskoˈbaldi]; also Gerolamo, Girolimo, and Geronimo Alissandro; September, 1583 – 1 March 1643) was a musician from the Duchy of Ferrara, in what is now northern Italy. He was one of the most important composers of keyboard music in the late Renaissance and early Baroque periods. A child prodigy, Frescobaldi studied under Luzzasco Luzzaschi in Ferrara, but was influenced by many composers, including Ascanio Mayone, Giovanni Maria Trabaci, and Claudio Merulo. Girolamo Frescobaldi was appointed organist of St. Peter's Basilica, a focal point of power for the Cappella Giulia (a musical organisation), from 21 July 1608 until 1628 and again from 1634 until his death.

Frescobaldi's printed collections contain some of the most influential music of the 17th century. His work influenced Johann Jakob Froberger, Johann Sebastian Bach, Henry Purcell, and countless other major composers. Pieces from his celebrated collection of liturgical organ music, Fiori musicali (1635), were used as models of strict counterpoint as late as the 19th century.