Christoph Willibald Gluck (July 2, 1714 – November 15, 1787) was a German composer. He is seen as one of the most important opera composers of the Classical music era, and is particularly remembered for the opera Orfeo ed Euridice, the best known part of which is probably the Dance of the Blessed Spirits, a slow, soft melody for flute and orchestra. Gluck was born in Erasbach, Upper Palatinate, Bavaria, Germany to a forester in the service of a nobleman. He studied music and philosophy in Prague from the age of eighteen. He wrote his first opera, Artaserse in 1741, and began to compose very prolifically for the stage. His works at this time were quite conservative Italian opera seria. He began to travel widely across Europe and in 1754 he secured the post of Kapellmeister to Maria Theresa of Austria, and settled in Vienna.

In 1756, Pope Benedict XIV knighted Gluck and awarded him the Order of the Golden Spur. From that time on, Gluck used the title "Ritter von Gluck" or "Chevalier de Gluck".

While in Vienna, Gluck composed Orfeo ed Euridice (1762), one of his best known works, and the ballet Don Juan (1761). These both show some of the changes in style that were to reach full expression in Alceste (1767), which included a preface laying out his ideas on a new style of opera. Gluck's idea was to make the drama of the work more important than the star singers who performed it, and to do away with recitative which broke up the action. The more flowing and dramatic style which resulted has been seen as a precursor to the music dramas of Richard Wagner.

In his own time, however, Gluck's reforms were controversial. After a move to Paris in 1773, where he enjoyed the protection of Queen Marie Antoinette, and where Iphigénie en Aulide and several of his other works were produced, two camps amongst music critics emerged: one praising Gluck's new style, the other deprecating him, and instead supporting the more traditional works of Niccolò Piccinni. The composers themselves did not get involved with the polemics, but when Piccinni was asked to set a libretto that Gluck himself was known to be working on, Gluck destroyed what he had written so far.

Gluck revised both Orfeo ed Euridice and Alceste for Parisian productions, also translating them from the original Italian into French. After the premieres of Armide in 1777 and Iphigénie en Tauride in 1779, Gluck returned to Vienna. He continued to write some smaller works there, but largely retired. He died there in 1787, leaving around 35 completed operas, as well as several ballets and instrumental works. Gluck was also an important influence on Hector Berlioz who was a fan.

Christoph Willibald Gluck is buried in the Zentralfriedhof in Vienna, Austria.