In music, a whole-tone scale is a scale in which each note is separated from its neighbors by the interval of a whole tone. In twelve-tone equal temperament, there are only two complementary whole-tone scales, both six-note or hexatonic scales. A single whole-tone scale can also be thought of as a "six-tone equal temperament".

The whole-tone scale has no leading tone and because all tones are the same distance apart, "no single tone stands out, [and] the scale creates a blurred, indistinct effect". This effect is especially emphasised by the fact that triads built on such scale tones are all augmented triads. Indeed, all six tones of a whole-tone scale can be played simply with two augmented triads whose roots are a major second apart. Since they are symmetrical, whole-tone scales do not give a strong impression of the tonic or tonality.

Only two triads are possible, both of them augmented, and...all inversions sound alike. All 'progressions' tend to have the same tonal character. What one hears are tone centers rather than tonics, and only when they are stressed [emphasized], as by repetition or duration. It cannot be denied that the small number of possible different intervals [only even semitone intervals: 2, 4, 6, 8, 10] and nonequivalent chords available in the whole-tone scale results in a soft-edged, neutral kind of sound lacking in tonal contrast.... Since the 1930s...whole-tone harmony...has become one of the platitudes of the "Hollywood Style."

The composer Olivier Messiaen called the whole-tone scale his first mode of limited transposition. The composer and music theorist George Perle calls the whole-tone scale interval cycle 2, or C2. Since there are only two possible whole-tone-scale positions (that is, the whole-tone scale can be transposed only once), it is either C2⁰ or C2¹. For this reason, the whole-tone scale is also maximally even and may be considered a generated collection.

Due to this symmetry, the hexachord consisting of the whole-tone scale is not distinct under inversion or more than one transposition. Thus many composers have used one of the "almost whole-tone" hexachords, whose "individual structural differences can be seen to result only from a difference in the 'location', or placement, of a semitone within the otherwise whole-tone series." Alexander Scriabin's mystic chord is a primary example, being a whole-tone scale with one note raised a semitone; this alteration allows for a greater variety of resources through transposition.