Wilhelm Richard Wagner (; ; 22 May 181313 February 1883) was a German composer, theatre director, polemicist, and conductor who is primarily known for his operas (or, as some of his later works were later known, "music dramas"). Unlike most opera composers, Wagner wrote both the libretto and the music for each of his stage works. Initially establishing his reputation as a composer of works in the romantic vein of Weber and Meyerbeer, Wagner revolutionised opera through his concept of the ''Gesamtkunstwerk'' ("total work of art"), by which he sought to synthesise the poetic, visual, musical and dramatic arts, with music subsidiary to drama. He described this vision in a series of essays published between 1849 and 1852. Wagner realised these ideas most fully in the first half of the four-opera cycle ''Der Ring des Nibelungen'' (''The Ring of the Nibelung'').
His compositions, particularly those of his later period, are notable for their complex textures, rich harmonies and orchestration, and the elaborate use of leitmotifs—musical phrases associated with individual characters, places, ideas or plot elements. His advances in musical language, such as extreme chromaticism and quickly shifting tonal centres, greatly influenced the development of classical music. His ''Tristan und Isolde'' is sometimes described as marking the start of modern music.
Until his final years, Wagner's life was characterised by political exile, turbulent love affairs, poverty and repeated flight from his creditors. His controversial writings on music, drama and politics have attracted extensive comment since the late 20th century, especially where they express antisemitic sentiments. The effect of his ideas can be traced in many of the arts throughout the 20th century; his influence spread beyond composition into conducting, philosophy, literature, the visual arts and theatre.