Siegfried (Franz Johann Carl) Graf (from 1920, Fürst) von Clary und Aldringen (14 October 1848 – 11 February 1929) was an Austro-Hungarian diplomat during the time before World War I.

He was born in Teplitz (now Teplice) on 14 October 1848 into a prominent Bohemian noble family, the second son of Prince Edmund Moritz and Princess Elisabeth-Alexandrine von Clary-und-Aldringen (née Countess de Ficquelmont).

[1] In December 1902, Count von Clary-Aldringen was appointed to serve as Minister at Brussels and would remain there for eleven years until 1914.

Acting as the doyen of the diplomatic corps in Brussels and personally popular, it fell upon him to deliver the declaration of war on 28 August.

[3] In March 1920, he became the sixth Prince von Clary-Aldringen following his older brother Carlos' death and died in Teplitz on 11 February 1929.