A lead sheet is a form of music notation that specifies the essential elements of a popular song: the melody, lyrics and harmony. The melody is written in modern Western music notation, the lyric is written as text below the staff and the harmony is specified with chord symbols above the staff.

Together, the melody, lyrics and harmony define what a song is. In the music industry and entertainment law, a lead sheet is the document used to describe a song for legal purposes. For example, a lead sheet is the form of a song to which copyright is applied—if a songwriter sues someone for copyright violation, the court will compare lead sheets to determine how much of the song has been copied. Or if a song is considered for an Academy Award or a Grammy, the song is submitted for consideration in the form of a lead sheet.

The lead sheet does not describe the chord voicings, voice leading, bass line or other aspects of the accompaniment. These are specified later by an arranger or improvised by a performer, and are aspects of the arrangement or performance of a song, rather than a part of the song itself.