The Requiem Mass in D minor (K. 626) by Wolfgang Amadeus Mozart was composed in Vienna in 1791 and left unfinished at the composer's death on December 5. A completion dated 1792 by Franz Xaver Süssmayr was delivered to Count Franz von Walsegg, who had anonymously commissioned the piece for a Requiem Mass to commemorate the February 14 anniversary of his wife's death.