Separate but equal was a legal doctrine in United States constitutional law, according to which racial segregation did not necessarily violate the Fourteenth Amendment to the United States Constitution, which nominally guaranteed "equal protection" under the law to all people. Under the doctrine, as long as the facilities provided to each race were equal, state and local governments could require that services, facilities, public accommodations, housing, medical care, education, employment, and transportation be segregated by race, which was already the case throughout the states of the former Confederacy. The phrase was derived from a Louisiana law of 1890, although the law actually used the phrase "equal but separate".

Plessy v. Ferguson, 163 U.S. 537 (1896), was a landmark U.S. Supreme Court decision ruling that racial segregation laws did not violate the U.S. Constitution as long as the facilities for each race were equal in quality, a doctrine that came to be known as "separate but equal". The decision legitimized the many state laws re-establishing racial segregation that had been passed in the American South after the end of the Reconstruction era in 1877. Such legally enforced segregation in the south lasted into the 1960s.