SS-Sturmbannführer Karl Steubl, Steubel, or Steibel[1] (25 October 1910 – 21 September 1945) was a Nazi, perpetrator of euthanasia programme dubbed Action T4, and commander of transportation at the Sobibór extermination camp during Operation Reinhard, the most deadly phase of the Holocaust.

[2] Before his last assignment at Sobibor in occupied Poland, Steubl was a senior male nurse at Schloss Hartheim, the biggest mass extermination centre outside Eastern Europe set up at Alkoven in Upper Austria.

Already by August 1941, long before the war's end, a grand total of 18,269 mentally and physically handicapped patients including many others, were murdered at gas chambers of Hartheim Euthanasia Centre and cremated on site in the course of his service there.

[3][better source needed] Erich Bauer remarked: Steubel participated in gang rapes of female prisoners prior to killing them at Sobibór: I was blamed for being responsible for the death of the Jewish girls Ruth and Gisela, who lived in the so-called forester house.

I lived in the room above them and due to these celebrations could not fall asleep after coming back from a journey....[4]From August 1942, Steubl was one of the Austrian commanders of Sobibór extermination camp, which he also helped organize as an expert in gassing.