Eugenics aims at intergenerational human improvement through populational adjustments. From its origins in the last third of the nineteenth century, eugenics became a social movement with international reach during the first half of the twentieth century. Although the idea of eugenics often calls to mind Nazi Germany and its extensive practices of compulsory sterilization, euthanasia, and genocide during the short period between 1933 and 1945, eugenic practices and policies were widespread earlier in that century and continued beyond the fall of the Nazis. The focus of this chapter is on providing a basic understanding of eugenics and of the ways in which eugenic thinking has been manifest in medicine, healthcare, and bioethics over this longer stretch of time, with special attention to the relationship between eugenics and disability.