(Wilhelm) Richard Wagner was a German composer, theatre director, polemicist, and conductor who is primarily known for his operas. Unlike most composers, Wagner wrote both the libretto and the music for each of his stage works. Wagner revolutionized opera through his concept of the Gesamtkunstwerk, by which he sought to synthesize the poetic, visual, musical and dramatic arts, with music subsidiary to drama. Wagner realized these ideas most fully in the four-opera cycle Der Ring des Nibelungen (known as The Ring Cycle).

His compositions are notable for the use of leitmotifs—musical phrases associated with individual characters, ideas or plot elements. His advances in musical language greatly influenced the development of classical music.

The effect of his ideas can be traced in many of the arts throughout the 20th century; their influence spread beyond composition into conducting, philosophy, literature, the visual arts, and theatre.