Wozzeck (German pronunciation: [ˈvɔtsɛk]) is the first opera by Austrian composer Alban Berg and a landmark modernist opera, written 1914–1922 and premiered in 1925. Based on Georg Büchner's unfinished play Woyzeck (1836), it depicts a soldier's tragic slide into madness and murder amid militarism and oppression. Berg intensified the psychological drama with his innovative approach to musical form and Expressionist music, to which he added themes and topics related to fate and nature. A succès de scandale at its premiere, Wozzeck faced ideological backlash but remains a cornerstone of the repertoire, celebrated for its narrative power and complex musical structure.

Alban Berg wrote Wozzeck from 1914 to 1922, stalled partly by World War I. He wrote his own libretto after Junges Deutschland writer Georg Büchner's unfinished play Woyzeck (1836), inspired by its 5 May 1914 Vienna premiere. Editor Karl Emil Franzos misread the name Wozzeck from Büchner's challenging manuscript.

Trained in biology and medicine, Büchner (1813-1817) taught anatomy at the University of Zurich. As a writer, he stressed characterization over narrative. He had radical politics and studied the French Revolution for his first play, Danton's Death. It crushed him. History seemed grimly fixed against revolt. People were "froth on the waves", greatness coincidental, and genius futile under "iron law".

In Woyzeck, Büchner mixed the grotesque with tragicomedy. He used real cases of romantic femicide, mainly physician Johann Christian August Clarus's report on Johann Christian Woyzeck, a poor soldier from Leipzig. Despite a long medical history of mental disorders and psychosis, Woyzeck was found competent in 1821 and beheaded in 1824. When Büchner died of typhus, he left an untitled, fragmentary script with shifting character names.

Berg saw strange potential in this dark social criticism, perhaps after Richard Strauss's Salome or his mentor Arnold Schoenberg's Erwartung (Expectation). He used short interludes to bind scenes after Claude Debussy's Pelléas et Mélisande while retaining the jagged brutality and eerie realism of Büchner's work. He added bits of his life, a habit: scripted coughs echoed his asthma, and the Doctor's salamanders line mocked scientist and musician Paul Kammerer, the first failed love of his wife Helene [de].

Berg mainly used writer Paul Landau [de]'s Wozzeck–Lenz: Zwei Fragmente (1909, reprinted 1913; Insel–Verlag [de]), which reordered Franzos's 26 scenes. Theater director Arthur Rundt [de], whose cuts Berg mostly followed, had used it in 1914. That year, scholar Hugo Bieber [de] tied the play to Woyzeck the man. In 1919, scholar Georg Witkowski issued a critical edition. Franzos ruined Büchner's play with omissions, edits, and additions, he wrote.

Franzos's publisher lost rights, so Berg left the title. He mostly chose Franzos's freer, livelier text over Witkowski's. Franzos's form (exposition, development, catastrophe) shaped Berg's, whose staging and lighting showed time passing, adding to Franzos's flow ("The drama ... must go forward ... breathlessly", he replied to Hanns Heinz Ewers's 1925 offer to collaborate). Berg's epilogue, Marie's son trailing friends to her corpse, was mostly Franzos's invention.

Berg mostly focused on music but saw more subjugation than poverty in the tale, likely from his war service, which he wrote Schoenberg was "slavery" that might go on "for years" in 1917. "[T]he fate of this poor man [Wozzeck], exploited and tormented by all the world ... touches me", he wrote Webern in 1918. Publicly, he backed Alexander Landau's 1926 socialist view (Wozzeck's suffering is not his, but ours) and Otto Brües [de]'s 1929 Biblical view (suffering is from God).