The half diminished scale is a seven-note musical scale. It is more commonly known as the Locrian ♮2 scale^[1] or the Aeolian ♭5 scale, names that avoid confusion with the diminished scale and the half-diminished seventh chord (minor seventh, diminished fifth). It is the sixth mode of the ascending melodic minor scale.

In the key of B♭, the half-diminished scale built on C is associated with Cm^7♭5, which functions as a ii^ø7 chord in minor (see chord-scale system).