The Einsatzgruppen Trial (or, officially, The United States of America vs. Otto Ohlendorf, et al.) was the ninth of the twelve trials for war crimes the U.S. authorities held in their occupation zone in Germany in Nuremberg after the end of World War II. These twelve trials were all held before U.S. military courts, not before the International Military Tribunal, but took place in the same rooms at the Palace of Justice. The twelve U.S. trials are collectively known as the "Subsequent Nuremberg Trials" or, more formally, as the "Trials of War Criminals before the Nuremberg Military Tribunals" (NMT).

The Einsatzgruppen were SS mobile death squads, operating behind the front line in Nazi-occupied eastern Europe. From 1941 to 1943 alone, they murdered more than one million Jews and tens of thousands of "partisans", Roma, disabled persons, political commissars, and others. The 24 defendants in this trial were all officers of these Einsatzgruppen and faced mass murder charges. The tribunal stated in its judgment:

Einsatzgruppen (German: "task forces"; singular Einsatzgruppe; official full name Einsatzgruppen der Sicherheitspolizei und des SD) were SS paramilitary death squads that were responsible for mass killings, typically by shooting, of Jews in particular, but also significant numbers of other population groups and political categories. The Einsatzgruppen operated throughout the territory occupied by the German armed forces following the German invasions of Poland, in September, 1939, and later, of the Soviet Union on June 22, 1941. The Einsatzgruppen carried out operations ranging from the murder of a few people to operations which lasted over two or more days, such as the massacres at Babi Yar (33,771 killed in two days) and Rumbula (25,000 killed in two days). The Einsatzgruppen were responsible for the murders of over 1,000,000 people, and they were the first Nazi organizations to commence mass killing of Jews as an organized policy.

The Einsatzgruppen were formed under the direction of SS-Obergruppenführer Reinhard Heydrich (deputy to Heinrich Himmler) and operated by the Schutzstaffel (SS) before and during World War II. From September 1939 forward the SS-Reichssicherheitshauptamt (RSHA - Reich Main Security Office) had overall command of the Einsatzgruppen. Their principal task during the war (according to SS General Erich von dem Bach at the Nuremberg Trials) "... was the annihilation of the Jews, Gypsies, and Soviet political commissars". The Einsatzgruppen had a leading role in the implementation of the final solution of the Jewish question (Die Endlösung der Judenfrage) in the conquered territories.