The hypodorian mode, literally meaning 'below dorian', is a musical mode or diatonic scale of ancient Greece that was based upon the dorian tetrachord: a series of rising intervals of a semitone followed by two whole tones. The rising scale for the octave is a single tone followed by two conjoint dorian tetrachords. This is the same as playing all the white notes of a piano from A to A: A | B C D E | (E) F G A. Confusingly, this scale in mediaeval and modern music theory came to be known as the aeolian or minor mode.

The mediaeval music scholars, misunderstanding the Latin texts by Boethius of how the Greek modes were reckoned, used the term hypodorian to describe the second mode of church music. This mode is the plagal counterpart of the authentic first mode, which was dubbed dorian. The ecclesiastical hypodorian mode is based on the relative scale of 'white notes' from D to D, with the musical dominant, the reciting note, or tenor at the minor third on the scale (or F, in the D to D scale). The melodic range of the ecclesiastical hypodorian mode ranges from the perfect fourth below the tonic to the perfect fifth above.