Johann Niemann (4 August 1913 – 14 October 1943) was a German SS-Untersturmführer (Second Lieutenant) and deputy commandant of Sobibor extermination camp. Niemann directly perpetrated the genocide of Jews and other peoples at Sobibór during the Operation Reinhard phase of The Holocaust.
Niemann joined the Nazi Party in 1931 as member number 753,836 and the SS in 1934 as member number 270,600. He first served at Bełżec extermination camp, at the rank of SS-Oberscharführer (Staff Sergeant), where he commanded Camp II, the extermination area. He then was transferred to Sobibór extermination camp. Niemann was deputy commander of Sobibór on various occasions in 1942 before being given the position permanently in early 1943. After Heinrich Himmler's visit to Sobibór on 12 February 1943, Niemann was promoted to SS-Untersturmführer.
Karl Frenzel, also a commandant at Sobibór, recalled how Niemann handled a particular threat of prisoner revolt within the camp: A Polish Kapo told me that some Dutch Jews were organizing an escape, so I relayed it to Deputy Commandant Niemann. He ordered the seventy-two Jews to be executed. On 14 October 1943, a prisoner uprising took place throughout the Sobibór camp. Niemann was the highest-ranking SS officer who was on duty at the camp that day, and so he was the first person targeted to be assassinated by the prisoners. Niemann was killed in the tailor's barracks with an axe to his head by Alexander Shubayev, a Jewish Belorussian Red Army soldier who had been imprisoned at Sobibór as a prisoner of war.