An augmented triad is a chord which made up of two major thirds stacked on top of each other. The interval between the lowest note in the chord (the root) and the highest note in the chord (the fifth) is called an augmented fifth. The name augmented triad comes from the fact that an augmented triad is the same as a major chord whose top note (fifth) is raised, or "augmented". An augmented chord is indicated by the symbol "+" or "aug". For example, the augmented triad built on A♭, written as A♭+, has pitches A♭-C-E:

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

A major triad, such as C–E–G, contains a major third (C–E) and a minor third (E–G). This makes the interval between the root and the fifth of the chord (C–G) perfect. On the other hand, the augmented triad has an augmented fifth, or a perfect fifth raised by one semitone. For example, an augmented triad with the root note C would have the notes C–E–G♯. Augmented chords frequently appear as the three chord of a minor key, the one chord of a major key, the four chord of a major key, or the five chord of a major key. The root of the chord often remains stationary, goes down five scale degrees, or goes up four scale degrees. The third of the chord usually either goes up one scale degree or stays the same. The fifth of the chord often goes up one scale degree. An augmented triad also has inversions. A one augmented (I+) chord sometimes contains the major seventh interval, while the five augmented (V+) chord sometimes contain the minor seventh interval.

The augmented triad on the V may be used as a substitute dominant chord.^[1]

Examples of popular music songs featuring the augmented chord include in the introduction of Chuck Berry's "School Days", Aaron Neville's "Tell It Like It Is", The Beatles' "Oh! Darling", after intros in Gene Pitney's "Town Without Pity", The Beach Boys' "The Warmth of the Sun", Joe Cocker's "Delta Lady", and at the end of the bridge in Patience and Prudence's "Tonight You Belong to Me", The Caravelles' "You Don't Have to Be a Baby to Cry", The Beatles' "From Me to You", The Dave Clark Five's "Glad All Over", and Martha and the Vandellas' "Dancing in the Street".^[2]