The chaconne is a form of music.
Originally a kind of dance in a slow 3/4 time which first emerged in the 16th century and which is probably of Spanish provenance, the word was later applied to any work in 3/4 consisting of a set of variations over a never-changing bass (a ground bass). One of the best known examples is the chaconne from Johann Sebastian Bach's second partita for solo violin (the bass line is not always present in this work, but it is strongly implied). Bach's Goldberg Variations are also frequently reckoned to be a chaconne, although Bach did not explicitly label them as such. After the baroque period, the chaconne form was not often used, though the 32 Variations in C minor by Ludwig van Beethoven belong to the form.
The chaconne is almost identical with the passacaglia, except that in the passacaglia the repeated theme is not always in the bass.