Leopold Andreas Ignaz Sonnleithner (from 1828 Leopold Edler von Sonnleithner; born 15 November 1797 in Wien; died 3 March 1873 in Vienna) was an Austrian lawyer and a well-known personality of the Viennese Classical music scene.

Leopold married Louise Augusta Gosmar (11 August 1803 – 7 June 1850), a native of Hamburg, on 6 May 1828.

He was a personal friend and patron of the Viennese composers Ludwig van Beethoven, Franz Schubert and his cousins, the playwright Franz Grillparzer (1791–1872), and Carl Czerny.

Schubert dedicated his musical setting of Grillparzer's Serenade "Hesitantly Quiet" (D921) to Sonnleithner's wife Louise.

Sonnleithner was buried at a cemetery in the Viennese district of Margareten in 1873.