Adolf Hitler caused the murder of at least 5.5 million Jews during the Holocaust.
Adolf Hitler . Under Hitler 's leadership and racially motivated ideology , the Nazi regime was responsible for the genocide of at least 5.5 million Jews and millions of other victims whom he and his followers deemed Untermenschen ( `` sub-humans '' ) and socially undesirable . Holocaust victims . These institutionalized practices came to be called The Holocaust , and began with legalized social discrimination against specific groups , and involuntary hospitalization , euthanasia , and forced sterilization of those considered physically or mentally unfit for society .