The Fantasy for piano, vocal soloists, mixed chorus, and orchestra, Op. 80, usually called the Choral Fantasy, was composed in 1808 by then 38-year-old Ludwig van Beethoven.

Beethoven intended the Fantasy to serve as the concluding work for the benefit concert he put on for himself on 22 December 1808; the performers consisted of vocal soloists, mixed chorus, an orchestra, and Beethoven himself as piano soloist. The Fantasy was designed to include all the participants in the program and thus unites all of these musical forces.

The work is noted as a precursor to the later Ninth Symphony.

The Fantasia was first performed at the Akademie of 22 December 1808, a benefit concert which also saw the premieres of the Fifth and Sixth Symphonies and the Fourth Piano Concerto as well as a performance of excerpts of the Mass in C major. To conclude this memorable concert program, Beethoven wanted a "brilliant finale" that would unite in a single piece the different musical elements highlighted in the concert night: piano solo, mixed chorus and orchestra. The Fantasia, Op. 80, written shortly before, was thus composed expressly to fulfil this role. Beethoven himself played the piano part and the opening solo offers an example of his improvisational style (at the premiere he did, in fact, improvise this section).

Beethoven wrote the piece during the second half of December 1808 in an unusually short time by his standards. He commissioned a poet—whose identity is disputed—to write the words shortly before the performance to fit the already written parts. According to Beethoven's pupil Carl Czerny, the poet was Christoph Kuffner [de], but the later Beethoven scholar Gustav Nottebohm doubted this attribution and suggested it may have been Georg Friedrich Treitschke, who in 1814 prepared the final text of Beethoven's opera Fidelio.

The premiere performance seems to have been a rather troubled one; according to the composer's secretary, Anton Schindler, it "simply fell apart", a result most likely attributable to insufficient rehearsal time. Because of a mistake in the execution of the piece, it was stopped halfway through and restarted. In Ignaz von Seyfried's words:

When the master brought out his orchestral Fantasia with choruses, he arranged with me at the somewhat hurried rehearsal, with wet voice-parts as usual, that the second variation should be played without repeat. In the evening, however, absorbed in his creation, he forgot all about the instructions which he had given, repeated the first part while the orchestra accompanied the second, which sounded not altogether edifying. A trifle too late, the Concertmaster, Unrath, noticed the mistake, looked in surprise at his lost companions, stopped playing and called out dryly: 'Again!' A little displeased, the violinist Anton Wranitzky asked 'With repeats?' 'Yes', came the answer, and now the thing went straight as a string.

The work includes a sequence of variations on a theme that is widely felt to be an early version of a far better known variation theme, namely the one to which Beethoven set the words of Friedrich Schiller's "Ode to Joy" in his Ninth Symphony. The two themes are compared below.