In music the root (basse fondamentale) of a chord is the note or pitch upon which that chord is perceived or labelled as being built or hierarchically centered upon. This feeling of centeredness is readily aurally perceivable for the culturally trained (those who grew up with European music) and its verbal labelling is a basic skill for the musically trained.

When the root is the bass note, or bottom, of the chord the chord is said to be in root position. This may also be described as uninverted or as in normal form. Often the root is not actually the lowest pitch being played in a chord, in which case the chord is inverted. See: figured bass.

Conventionally, the name of the note which is the root is used to denote the chord, thus a major chord built on C is a C Major chord. Since Rameau, the analysis and theory of tonal music usually treats the roots as the defining feature of chords and much information can be gained from a progression of roots even if chord types are unknown. Also, if the key is known then the chord forms are known for each root.

A root progression is the most familiar form of labelling chord progressions by their root, rather than bass if different, and is in contrast to an older pre-tonal conception of chords as sonorities, with a root position or first inversion triad being simply alternative and fairly equivalent ways of "filling in" the consonance between octaves, C (E G) C or C (F A) C.