Racial hygiene was a set of state-sanctioned policies in the early twentieth century by which certain groups of individuals were allowed to procreate and others not, with the expressed purpose of promoting characteristics deemed desirable. The most extensive implementation of such policies occurred in Nazi Germany but similar policies were implemented throughout Europe, North America and Southern Africa.

The concept of racial purity was developed by Arthur de Gobineau, who argued that race created culture and that race-mixing leads to chaos. Racial hygiene was historically tied to traditional notions of public health, but usually with an enhanced emphasis on heredity. Francis Galton began working in 1869 to find a statistical science of heredity which he believed could encourage voluntary care in selecting partners, and in 1883 he introduced the term "eugenics" for this subject, but in the early 20th century a eugenics movement adopted ideas of Mendelian genetics and promoted negative eugenics to prevent those thought to be unsuitable from having children, and eugenics was used to legitimise policies of racial hygiene.