Girolamo Dalla Casa (d.1601) was an Italian composer, instrumentalist, and writer of the late Renaissance. He was a member of the Venetian School, and was perhaps more famous and influential as a performer than as a composer.

Nothing is known about his life prior to his arrival at Venice, but he was probably born at Udine sometime before the middle of the 16th century. He was first hired by the musical establishment of St. Mark's in 1568, along with his two brothers, Giovanni and Nicolò, where they formed the first permanent instrumental ensemble. The sonorous acoustical environment of this basilica was the center of activity of the Venetians. Giovanni Gabrieli clearly had his group in mind for much of his music, and the Dalla Casas must have played in many the elaborate polychoral compositions of the time.

The use of the Dalla Casas by Gabrieli and St. Mark's foreshadowed, and may have influenced, the development of the concertino -ripieno style of the concerto grosso in the later Baroque. Being a smaller group of virtuoso instrumentalists playing in contrast to larger instrumental and vocal forces arrayed around them, and being in the center of a hugely influential stylistic movement, they functioned as an early form of concertino. Much of the music which Gabrieli and the other Venetians wrote for them survives.

Two books of madrigals and one book of motets survive from his compositional output, which probably was not large. More important to musicology, however, was his two-part 1584 treatise on ornamentation (Il vero modo di diminuir), which gives clear and precise examples of ornamentation as it was practiced in singing and playing motets and madrigals at the time. From this treatise it is clear that polyphonic works were usually performed unadorned, but works in a more homophonic style, and especially grand polychoral works with frequent sectional changes and prominent cadences, were embellished with ornaments, few of which appear in the actual notated music.