Wozzeck is an opera by the Austrian composer Alban Berg (1885-1935). It was composed between 1914 and 1922 and first performed in 1925.
Berg wrote this opera before the period when he used serialism in his works. His teacher Schoenberg had not yet developed the twelve tone system. The music of Wozzeck has tonal music in the tradition of Mahler, but also some atonal music (music which is not based on any key) as well as melodies which are based on the whole tone scale. The music sounded very modern at the time it was written. Berg also writes for the voices in unusual ways: sometimes they have to half-speak, half-sing (this is called Sprechgesang).
The opera is based on a play called Woyzeck by the German playwright Georg Büchner. Woyzeck was an unusual drama because, instead of being a story about someone important such as a king or a god, it was about a poor man who is not very smart and is bullied and misused by other people. When Berg wrote the opera nearly a century later, it was still an unusual story for an opera. The heroes in operas were usually important people, while working people often had comic parts: they were often servants. But Wozzeck is a simple man who cannot help what is happening to him. In drama this is sometimes called an "anti-hero".