Giulio Fiesco was an Italian composer of the Renaissance, active in Ferrara, known for his madrigals. He was the first composer to set the poetry of Giovanni Battista Guarini, the most often-set poet by madrigalists of the late 16th century, and was an important court composer for the rich musical establishment of the Este family in Ferrara. All of Fiesco's surviving works are secular and vocal. He published four books of madrigals, in 1554, 1563, 1567, and 1569, dedicating all four to members of the Este family. Of these four books, the first and last have gotten the most attention. His compositions in the first book of 1554 show most directly the influence of Cipriano de Rore, the most renowned mid-century composer of madrigals, who was then the maestro di cappella in Ferrara for Duke Ercole II d'Este. Fiesco's compositions in this book are for four voices, and include madrigals in the classic style, chromatically experimental works (for example Bacio soave, which shows also the influence of Nicola Vicentino, who actively encouraged such experiments), as well as music likely intended for performance at dramatic events staged for the Este family. Poetry he sets includes works by Boccaccio, Giovanni Batista Strozzi, Bernardo Tasso, Sannazaro, Ludovico Ariosto, and Petrarch. Fiesco's last book of madrigals, the Musica nuova, for five voices, is his most famous, for it is the first appearance of the poetry of Guarini set to music. Fourteen out of the fifteen poems in the collection are sonnets, and the style matches the elegance of the language, attaining considerable virtuosity in text setting. Some of the settings are innovative harmonically and rhythmically, with one madrigal,S'armi pur d'ira disdegnoso ed empio, foreshadowing the Baroque stile concitato of rapid declamation over a homophonic texture. Not all of Fiesco's works are madrigals. He published a few secular songs in lighter current forms such as the greghesca and the napolitane, forms of Venetian and Neapolitan origin respectively.