The Concerto for Orchestra is one of Béla Bartók's best known pieces, and usually regarded as one of his best.

It was written in response to a commission from the Koussevitzky Foundation (run by the conductor Serge Koussevitzky) following Bartók's move to the United States from his native Hungary from where he had fled because of World War II. It has been speculated that Bartók's previous work, the String Quartet No. 6 (1939), could well have been his last were it not for this commission, which sparked a small number of other compositions, including the Sonata for solo violin and the Piano Concerto No. 3 .

The piece was written in 1943, the score being inscribed "15 August - 8 October 1943". It was premiered on December 1, 1944, in Boston, Massachusetts by the Boston Symphony Orchestra conducted by Serge Koussevitzky. It was a great success, and has been regularly performed since.

Bartók revised the piece in February 1945, the biggest change coming in the last movement, where he wrote a longer ending. Both verions of the ending were published, and both versions are performed today.

The piece is in five movements:

1. Introduzione - a slow and mysterious introduction gives way to an allegro with numerous fugal passages.
2. Giuoco delle coppie (Game of pairs) - this movement prominently features the side drum which taps out a rhythm at the beginning and end of the movement. In between, pairs of wind instruments play short passages. In each passage a different interval separates the pair - bassoons are a minor sixth apart, oboes are in thirds, clarinets in sevenths, flutes in fifths and trumpets in seconds.
3. Elegia - a slow movement, typical of Bartók's so-called "night music".
4. Intermezzo interrotto (Interrupted intermezzo) - a flowing melody in with chaning time signatures is interrupted by a brash parody of the repeated theme from Dmitri Shostakovich's Symphony No. 7 featuring glissandi on the trombones and "laughing" woodwinds.
5. Finale - marked presto (fast), this is in parts a perpetuum mobile.

This is the best known of a number of pieces to have the apparently contradictory title Concerto for Orchestra. Bartók said that he called the piece a concerto rather than a symphony because of the way the instruments are treated in a solistic and virtuosic way.