Karl Siegmund von Seckendorff (26 November 1744 – 26 April 1785) was a German military officer, poet, and composer.
He was born in Erlangen, Bavaria, the son of a Bavarian margrave and part of the Franconian aristocratic family Seckendorff.
In Weimar, he supervised the Hofkapelle, and there began to pursue his literary and artistic ideas.
He wrote a music monodrama entitled Proserpina (produced in Weimar, 1778), whose success was due to Goethe.
Disappointed with his lack of success, in 1784, he moved to Ansbach to become the Prussian ambassador to the Franconian Circle.