Racial segregation is separation of humans into racial groups in daily life. It may apply to activities such as eating in a restaurant, drinking from a water fountain, using a public toilet, attending school, going to the movies, or in the rental or purchase of a home. Segregation itself is defined by the European Commission against Racism and Intolerance as "the act by which a (natural or legal) person separates other persons on the basis of one of the enumerated grounds without an objective and reasonable justification, in conformity with the proposed definition of discrimination. As a result, the voluntary act of separating oneself from other persons on the basis of one of the enumerated grounds does not constitute segregation". According to the UN Forum on Minority Issues, "The creation and development of classes and schools providing education in minority languages should not be considered impermissible segregation, if the assignment to such classes and schools is of a voluntary nature".

Racial segregation is generally outlawed, but may exist through social norms, even when there is no strong individual preference for it, as suggested by Thomas Schelling's models of segregation and subsequent work. Segregation may be maintained by means ranging from discrimination in hiring and in the rental and sale of housing to certain races to vigilante violence (such as lynchings, e.g.) Generally, a situation that arises when members of different races mutually prefer to associate and do business with members of their own race would usually be described as separation or de facto separation of the races rather than segregation. In the United States, legal segregation was required in some states and came with "anti-miscegenation laws" (prohibitions against interracial marriage). Segregation, however, often allowed close contact in hierarchical situations, such as allowing a person of one race to work as a servant for a member of another race. Segregation can involve spatial separation of the races, and mandatory use of different institutions, such as schools and hospitals by people of different races.