The white genocide, white extinction, or white replacement conspiracy theory is a white supremacist conspiracy theory that claims there is a deliberate plot to cause the extinction of whites through forced assimilation, mass immigration, and/or violent genocide. It purports that this goal is advanced through the promotion of miscegenation, interracial marriage, mass non-white immigration, racial integration, low fertility rates, abortion, pornography, LGBT identities, governmental land-confiscation from whites, organised violence, and eliminationism in majority white countries. Under some theories, Black people, Hispanics, and Muslims are blamed for the secret plot, but usually as more fertile immigrants, invaders, or violent aggressors, rather than as the masterminds. A related, but distinct, conspiracy theory is the Great Replacement theory.

White supremacy 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.