White supremacy or white supremacism is the belief that white people are superior to those of other races and thus should dominate them. The belief favors the maintenance and defense of any power and privilege held by white people. White supremacy has roots in the now-discredited doctrine of scientific racism and was a key justification for European colonialism. It underlies a spectrum of contemporary movements including neo-Confederates, neo-Nazism and the so-called Christian Identity movement.Different forms of white supremacy put forth different conceptions of who is considered white, though the exemplar is generally light-skinned, blond-haired, and blue-eyed—traits most common in northern Europe, which are pseudoscientifically viewed as being part of an Aryan race. Different groups of white supremacists identify various racial, ethnic, religious, and other enemies, most commonly those of Sub-Saharan African ancestry, Indigenous peoples of the Americas and Oceania, Asians, multiracial people, Middle Eastern people, Jews, Muslims, and LGBTQ+ people.

As a political ideology, it imposes and maintains cultural, social, political, historical, and/or institutional domination by white people and non-white supporters. This ideology has been put into effect through socioeconomic and legal structures such as the Atlantic slave trade, Jim Crow laws in the United States, the White Australia policies from the 1890s to the mid-1970s, and apartheid in South Africa. In addition, this ideology is embodied in the "White power" social movement. Since the early 1980s, the White power movement has been committed to overthrowing the United States government and establishing a white ethnostate using paramilitary tactics.In academic usage, particularly in critical race theory or intersectionality, "white supremacy" can also refer to a social system in which white people enjoy structural advantages (privilege) over other ethnic groups, on both a collective and individual level, despite formal legal equality.