During World War II, Reichskommissariat Ukraine (abbreviated as RKU) was the civilian occupation regime of much of Nazi German-occupied Ukraine (which included adjacent areas of modern-day Belarus and pre-war Second Polish Republic). It was governed by the Reich Ministry for the Occupied Eastern Territories headed by Alfred Rosenberg. Between September 1941 and August 1944, the Reichskommissariat was administered by Erich Koch as the Reichskommissar. The administration's tasks included the pacification of the region and the exploitation, for German benefit, of its resources and people. Adolf Hitler issued a Führer Decree defining the administration of the newly occupied Eastern territories on 17 July 1941.

Before the German invasion, Ukraine was a constituent republic of the Soviet Union, inhabited by Ukrainians with Russian, Romanian, Polish, Jewish, Belarusian, German, Romani and Crimean Tatar minorities. It was a key subject of Nazi planning for the post-war expansion of the German state. The Nazi extermination policy in Ukraine, with the help of local Ukrainian collaborators, ended the lives of millions of civilians in The Holocaust and other Nazi mass killings: it is estimated 900,000 to 1.6 million Jews and 3 to 4 million non-Jewish Ukrainians were killed during the occupation; other sources estimate that 5.2 million Ukrainian civilians (of all ethnic groups) perished due to crimes against humanity, war-related disease, and famine amounting to more than 12% of Ukraine's population at the time.