The Generalplan Ost, abbreviated GPO, was Nazi Germany's blueprint for the genocide, extermination and large-scale ethnic cleansing of Slavs, Eastern European Jews, and other indigenous peoples of Eastern Europe categorized as "Untermensch" in Nazi ideology. The campaign was a precursor to Nazi Germany's planned colonisation of Central and Eastern Europe by Germanic settlers, and it was carried out through systematic massacres, mass starvations, chattel labour, mass-rapes, child abductions, and sexual slavery.

Ethnic cleansing is the systematic forced removal of ethnic, racial, or religious groups from a given area or population itself, with the intent of making the society ethnically heterogeneous. Along with direct removal such as deportation or population transfer, it also includes indirect methods aimed at forced migration by coercing the victim group to flee and preventing its return, such as murder, rape, and property destruction. Both the definition and charge of ethnic cleansing is often disputed, with some researchers including and others excluding coercive assimilation or mass killings as a means of depopulating an area of a particular group.