Miserere by Gregorio Allegri is a piece of a cappella religious music (a setting of Psalm 50/51) composed during the reign of Pope Urban VIII, probably during the 1630s, for use in the Sistine Chapel during matins on Wednesday and Friday of Holy Week. It was the last of twelve Miserere settings composed and chanted at the service since 1514 and the most popular: at some point, it became forbidden to transcribe the music and it was only allowed to be performed at those particular services, adding to the mystery surrounding it. Writing it down or performing it elsewhere would be punished by excommunication.

Although there were a handful of supposed transcriptions in various royal courts in Europe, none of them ever succeeded in capturing the beauty of the Miserere as performed annually in the Sistine Chapel. According to the popular story, a twelve-year-old Mozart was visiting Rome, when he first heard the piece during the Wednesday service. Later that day, he wrote it down entirely from memory, returning with it to the Chapel that Friday to make some minor corrections. Some time during his travels, he ran into the British historian Dr. Charles Burney, who got the piece from him and took it to London, where it was published. Once it was published, the ban was lifted, and Allegri's Miserere has since been one of the most popular a cappella choral works now performed.