Franz Xaver Süssmayr (German: Franz Xaver Süßmayr or Suessmayr in English; 1766 – September 17, 1803) was an Austrian composer and conductor. Popular in his day, he is now known for his completion of Wolfgang Amadeus Mozart’s Requiem in D Minor. In addition, there have been performances of Süssmayr’s operas at Kremsmünster, and a new version of his cantata "Der Retter in Gefahr" was performed. There are also CD recordings of his unfinished clarinet concerto (completed by Michael Freyhan), one of his German requiems, and his Missa Solemnis in D.