Gregorio Allegri (1582 7 February 1652) was an Italian composer and priest of the Roman School of composers. He lived mainly in Rome, where he would later die.

By far the most celebrated composition of Allegri is the Miserere mei, Deus, a setting of Vulgate Psalm 51. It is written for two choirs, the one of five and the other of four voices, and has obtained considerable celebrity. One of the choirs sings a simple fauxbordon based on the original plainsong chant for the Tonus peregrinus; the other choir sings a similar fauxbordon with pre-existing elaborations and the use of cadenzas. The Miserere has for many years been sung annually during Holy Week in the Sistine Chapel. Many have cited this work as an example of the stile antico or prima pratica. However, its constant use of the dominant seventh chord and its emphasis on polychoral techniques certainly put it out of the range of "prima pratica". A more accurate comparison would be to the works of Giovanni Gabrieli.