Piano Concerto No. 24 in C minor, K. 491, is a concerto for keyboard (usually a piano or fortepiano) and orchestra composed by Wolfgang Amadeus Mozart. Mozart composed the concerto in the winter of 1785-1786, finishing it on 24 March 1786, three weeks after the completion of the Piano Concerto No. 23 (K. 488) in A major. He premiered the work in early April 1786 at the Burgtheater in Vienna.
The work is one of only two minor-key piano concertos that Mozart composed, the other being the No. 20 (K. 466) in D Minor. None of Mozart's other piano concertos features a larger array of instruments: the work is scored for strings, woodwinds, horns, trumpets and timpani. The concerto consists of three movements. The first, Allegro, is in sonata form and is the longest opening movement for a concerto that Mozart had hitherto composed. The second movement, Larghetto, is in the relative major of E flat and features a strikingly simple principal theme. The final movement, Allegretto, returns to the home key of C minor and presents a theme followed by eight variations.
The work is one of Mozart's most advanced compositions in the concerto genre. Its early admirers included Ludwig van Beethoven and Johannes Brahms. Musicologist Arthur Hutchings considered it to be Mozart's greatest piano concerto.