Symphony No. 7 in D major, K. 45, by Wolfgang Amadeus Mozart, was completed in Vienna in January 1768 after the family's return from a visit to Olomouc and Brno in Moravia. The symphony is in four movements. Its first performance was probably at a private concert. The symphony was reworked to become the overture to Mozart's opera, La finta semplice, K. 51, composed and performed later that year, and the overture itself was subsequently adapted further to create a new symphony, known in the Köchel 1964 (K6) catalogue as K. 46a. The autograph of the score is preserved in the Staatsbibliothek Preusischer Kulturbesitz in Berlin.
For the original (K. 45) version the instrumentation was: strings, 2 oboes, 2 horns, 2 trumpets, timpani, bassoon, continuo. For the symphonic overture (K. 46a) version the trumpets were replaced with flutes, an extra bassoon was added, and the timpani were excised.
According to analyst Neal Zaslaw, the first occasion on which the K. 45 version could have been heard was a concert given by Prince von Galitzin, the Russian ambassador, at his Vienna residence in late March, 1768. The K. 46b version was heard at the premiere of La finta semplice, at Salzburg on 1 May 1769.