The Chantilly Codex (Chantilly, Musée Condé MS 564) is a manuscript of medieval music containing pieces from the style known as the Ars subtilior. It is held in the museum at the Château de Chantilly in Chantilly, Oise.

Most of the compositions in the Chantilly Codex date from c. 1350–1400. There are 112 pieces total, mostly by French composers, and all of them polyphonic. The codex contains examples of many of the most popular courtly dance styles of its time, such as ballades, rondeaus, virelais, and isorhythmic motets. Some of the motets are rhythmically extremely complex, and are written in intricately exact musical notation. Two pieces by Baude Cordier were added at a slightly later date at the front of the manuscript, and use unusual shapes to reflect their musical contents. The piece "Belle, Bonne, Sage, Plaisant" (image right) was written to a special lady for the New Year, and reflects the shape of the notation with the text (Lovely, good, wise, and pleasant). The graphic layout of the notation is a play on words on the "Cor" ("heart") in "Cordier".

The Chantilly Codex is known to contain music from the composers Johannes Symonis, Jehan Suzay, P. des Molins, Goscalch, Solage, Baude Cordier, Grimace, Guillaume de Machaut, Jehan Vaillant, F. Andrieu, Magister Franciscus, Johannes Cuvelier, Rodericus, Trebor, and Jacob Senleches.