These are the Oscar nominated films that revolve around the presentation of real world genocide.

The United Nations Genocide Convention defines a genocide as "any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such: killing members of the group; causing serious bodily or mental harm to members of the group; deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part; imposing measures intended to prevent births within the group; [and] forcibly transferring children of the group to another group"

Be it the Holocaust, the Rwandan Genocide, the Cambodian Genocide, or any other real world genocide, these films explore the trauma and tragedy of these real world genocides.

It should be noted, that these films focus primarily on or deal directly with the genocide aspect. Meaning for example, though there were many Oscar nominated films in the 40's and 50's that dealt with World War II, very few of these dealt specifically with the Holocaust and the treatment of the Jews, so most of them are not included. To give a specific example, the 2004 film Downfall is outright a biopic about Adolf Hitler, but it never mentions the Holocaust, so it is not included on the list.