Guillaume de Machaut (French: [gijom də maʃo]; sometimes spelled Machault; c. 1300 – April 1377) was a medieval French poet and composer. He is one of the earliest composers on whom significant biographical information is available. According to Daniel Leech-Wilkinson, Machaut was "the last great poet who was also a composer". Well into the 15th century, Machaut's poetry was greatly admired and imitated by other poets, including Geoffrey Chaucer.
Machaut composed in a wide range of styles and forms. He is a part of the musical movement known as the ars nova. Machaut helped develop the motet and secular song forms (particularly the lai and the formes fixes: rondeau, virelai and ballade). Machaut wrote the Messe de Nostre Dame, the earliest known complete setting of the Ordinary of the Mass attributable to a single composer.
Guillaume de Machaut was born about 1300, and educated in the region around Reims. His surname most likely derives from the nearby town of Machault, 30 km northeast of Reims in the Ardennes region. He was employed as secretary to John I, Count of Luxembourg and King of Bohemia from 1323 to 1346, and also became a canon (1337). He often accompanied King John on his various trips, many of them military expeditions around Europe (including Prague). He was named the canon of Verdun in 1330, Arras in 1332, and Reims in 1337. By 1340, Machaut was living in Reims, having relinquished his other canonic posts at the request of Pope Benedict XII. In 1346, King John was killed fighting at the Battle of Crécy, and Machaut, who was famous and much in demand, entered the service of various other aristocrats and rulers, including King John's daughter Bonne (who died of the Black Death in 1349), her sons Jean de Berry and Charles (later Charles V, Duke of Normandy), and others such as Charles II of Navarre.