Arnold Schoenberg or Schönberg (German: [ˈaːʁnɔlt ˈʃøːnbɛʁk] ( ); 13 September 1874 – 13 July 1951) was an Austrian composer and painter, associated with the expressionist movement in German poetry and art, and leader of the Second Viennese School. With the rise of the Nazi Party, by 1938 Schoenberg's works were labelled as degenerate music because he was Jewish (Anon. 1997–2013); he moved to the United States in 1934.

Schoenberg's approach, both in terms of harmony and development, has been one of the most influential of 20th-century musical thought. Many European and American composers from at least three generations have consciously extended his thinking, whereas others have passionately reacted against it.