Sir John Chandos, Viscount of Saint-Sauveur in the Cotentin, Constable of Aquitaine, Seneschal of Poitou, KG (c.1320 " 31 December 1369) was a medieval English knight who hailed from Radbourne Hall, Derbyshire. Chandos was a close friend of Edward, the Black Prince and a founding member and 19th Knight of the Order of the Garter in 1348. Chandos was a gentleman by birth, but unlike most commanders of the day he held no inherited title of nobility.

Described by the medieval historian Froissart as "wise and full of devices", as a military strategist Chandos is believed to have been the mastermind behind three of the most important English victories of the Hundred Years War: the Battle of Crécy, the Battle of Poitiers and the Battle of Auray. His death in a minor skirmish was regretted by both sides.