The augmented seventh chord, or seventh augmented fifth chord,^[1] or seventh sharp five chord is a seventh chord composed of a root, major third, augmented fifth, and minor seventh (1, 3, ♯5, ♭7).^[2] It can be viewed as an augmented triad with a minor seventh.^[3] When using popular-music symbols, it is denoted by +⁷, aug⁷,^[2] or ^7♯5. For example, the augmented seventh chord built on A♭, written as A♭+⁷, has pitches A♭-C-E-G♭:

The chord can be represented by the integer notation {0, 4, 8, 10}.

The root is the only optional note in an augmented seventh chord, the fifth being required because it is raised.^[4] This alteration is useful in the major mode because the raised 5th creates a leading tone to the 3rd of the tonic triad.^[3] See also dominant.

In rock parlance, the term augmented seventh chord is sometimes confusingly and erroneously used to refer to the so-called "Hendrix chord", a 7♯9 chord which contains the interval of an augmented ninth but not an augmented fifth.^[5]

The augmented minor seventh chord may be considered an altered dominant seventh and may use the whole tone scale, as may the dominant seventh flat five chord.^[7] See chord-scale system.

The augmented seventh chord normally resolves to the chord a perfect fifth below.^[8] Thus, G aug⁷ resolves to a C major or minor chord, for example.

• Augmentation (music)