Technologies available since the 1970s have enabled parents to influence the genetic makeup of their children. As the twenty-first century unfolds, emerging technologies—including gamete selection, gene editing, and in vitro gametogenesis—may allow greater control over heredity. These technologies have been criticized for involving “eugenics.” However, it is often not clear what this criticism amounts to. What is eugenics and/or why it is a bad thing? This chapter provides a conceptual analysis of “eugenics” and discusses its relevance to debates about twenty-first-century reproductive technologies. We argue for the plausibility of a broad definition of eugenics as “an attempt to improve heredity.” Whereas most common usages of reproductive genetic technologies fall under this broad definition, this alone does not entail they are morally problematic. Indeed, there will often be moral reasons to pursue eugenic aims. We conclude by discussing the types of practices that may be justified in the name of eugenics.