The Symphony No. 38 in D major, K. 504, was composed by Wolfgang Amadeus Mozart in late 1786. It premiered in Prague on January 19, 1787, during Mozart's first visit to the city. Because it was first performed in Prague, it is popularly known as the Prague Symphony. Mozart's autograph thematic catalogue records December 6, 1786, as the date of completion for this composition.

The Köchel catalogue is a chronological catalogue of compositions by Wolfgang Amadeus Mozart, originally created by Ludwig Ritter von Köchel, in which the entries are abbreviated K. or KV. Its numbers reflect the ongoing task of compiling the chronology of Mozart's works, and provide a shorthand reference to the compositions.