Anton Friedrich Wilhelm von Webern (3 December 1883 – 15 September 1945), better known as Anton Webern (German: [ˈantoːn ˈveːbɐn] (listen)), was an Austrian composer whose music was among the most radical of its milieu in its sheer concision, even aphorism, and steadfast embrace of then novel atonal and twelve-tone techniques. With his mentor Arnold Schoenberg and his colleague Alban Berg, Webern was at the core of those within the broader circle of the Second Viennese School. Little known in the earlier part of his life, not only as a student and follower of Schoenberg, but also as a peripatetic and often unhappy theater music director with a mixed reputation for being a demanding conductor, Webern came to some prominence and increasingly high regard as a vocal coach, choirmaster, conductor, and teacher during Red Vienna. With Schoenberg away at the Prussian Academy of Arts (and with the benefit of a publication agreement secured through Universal Edition), Webern began writing music of increasing confidence, independence, and scale during the latter half of the 1920s—his mature chamber and orchestral works, music that, perhaps more than his earlier expressionist works, would later decisively influence a generation of composers. Amid Austrofascism, Nazism, and World War II, Webern remained nevertheless committed to taking the "path to the new music", as he styled it in a series of private lectures delivered in 1932–1933 (but unpublished until 1960). He continued writing some of his most mature and later celebrated music while increasingly ostracized from official musical life as a "cultural Bolshevist", taking occasional copyist jobs from his publisher as he lost students and his conducting career.

Posthumously Webern's work became celebrated and influential, yet intimate understanding of its full context was fledgling and impracticable after years of suppression, neglect, or opposition and, moreover, severe disruption. The thread of his work was taken by composers in often formalist directions far beyond any residual post-Romanticism and expressionism that had remained in his style. His gradual innovations in schematic organization of pitch, rhythm, register, timbre, dynamics, articulation, and melodic contour; his later adaptation and generalization of imitative contrapuntal techniques such as canon and fugue; and his inclination toward athematicism, abstraction, and lyricism variously informed and oriented European, typically serial or avant-garde composers such as Luigi Dallapiccola, Olivier Messiaen, Pierre Boulez, Karlheinz Stockhausen, Luigi Nono, Bruno Maderna, Henri Pousseur, Bernd Alois Zimmermann, and György Ligeti. Later, both Brian Ferneyhough and Helmut Lachenmann also found much in Webern on the way to complexity in the case of the former and musique concrète instrumentale in the case of the latter, engaging particularly with his atonal works by some contrast to earlier post-Webernism. Less so in the United States, his music attracted the interest of Elliott Carter and Aaron Copland, whose critical ambivalence was marked by a certain enthusiasm and fascination nonetheless; Milton Babbitt, who ultimately derived more inspiration from Schoenberg's twelve-tone practice than that of Webern; and particularly Igor Stravinsky, to whom it was very fruitfully reintroduced by Robert Craft, and without which Stravinsky's late works might have taken different shape. Indeed, Stravinsky staked his contract with Columbia Records to see that Webern's "complete" music was first both recorded and widely distributed. Among the more interdisciplinary New York School, John Cage and Morton Feldman both cited the staggering effect of its sound on their own music, first meeting at a performance of Webern's Symphony and even singing the praises of Christian Wolff distinctly as "our Webern". A richer and more historically informed understanding of Webern and his music began to emerge during the latter half of the 20th century onward in the work of Kathryn Bailey Puffett, Allen Forte, Julian Johnson, Felix Meyer, and Anne Shreffler as archivists, biographers, and musicologists, most importantly Hans and Rosaleen Moldenhauer, gained access to sketches, letters, lectures, audio recordings, and other articles of or associated with Webern's estate.