Jazz standards are musical compositions which are an important part of the musical repertoire of jazz musicians, in that they are widely known, performed, and recorded by jazz musicians, and widely known by listeners. There is no definitive list of jazz standards, and the list of songs deemed to be standards changes over time. Songs included in major fake book publications (sheet music collections of popular tunes) and jazz reference works offer a rough guide to which songs are considered standards.
Not all jazz standards were written by jazz composers. Many are originally Tin Pan Alley popular songs, Broadway show tunes or songs from Hollywood musicals – the Great American Songbook. In Europe, jazz standards and "fake books" may even include some traditional folk songs (such as in Scandinavia) or pieces of ethnic music (such as ) that have been played with a jazz feel by well known jazz players. A commonly played song can only be considered a jazz standard if it is widely played among jazz musicians. The jazz standard repertoire has some overlap with blues and pop standards.
The most recorded jazz standard was W. C. Handy's "St. Louis Blues" for over 20 years from the 1930s onward, after which Hoagy Carmichael's "Stardust" replaced it. Today, the place is held by "Body and Soul" by Johnny Green. The most recorded standard composed by a jazz musician is Thelonious Monk's "'Round Midnight".