Sonnleithner, Joseph, b. Vienna, March 3, 1776, d. Vienna, Dec. 25, 1835, archivist and librettist. Son of Christoph Sonnleithner. 1804-1814 Secretary of the Court Theatre (Hoftheater); wrote a number of libretti (among others for "Leonore" by L. van Beethoven, "Faniska" by L. Cherubini and "Agnes Sorel" by A. Gyrowetz). S. was one of the founders of the Gesellschaft der Musikfreunde in Wien and one of the first collectors of Austrian folk-songs; a friend of F. Schubert and F. Grillparzer. Bibliographies, collection of musical instruments and artistic estate kept in the archives of the Gesellschaft der Musikfreunde in Vienna.