Government sponsored breeding programs, medals of motherhood, forced abortions, and surgical sterilization on park benches--all of these policies have come out of government efforts to nationalize sex and harness procreation as a tool of the state. Over 170 countries (or 85% of governments) worldwide have active policies designed to manipulate the fertility of their citizenry with the aim of influencing the rate of growth of their populations. While over 90% of least developed states are trying to combat population growth with policies designed to reduce fertility, over two-thirds of all developed countries are actively crafting legislation to increase their populations. Despite over a hundred years of relative failure and innumerable studies questioning the viability and utility of government attempts to manipulate the fertility rate of the population as a whole, the majority of governments worldwide continue to uphold and develop such policies. What drives government to try to control how many children people will have? Nationalizing Sex traces why population emerged as an object of governance and how natalist policy has changed over time and place, using case studies from France, Germany, Russia, India, and China. It analyzes the origins, growth, and development of fertility as a national and international political issue, the rise and fall of the narratives used to ascribe meaning to natality, and the global proliferation of oddly similar policies adopted by widely dissimilar states. As importantly, it explains why, after hundreds of years, countries continue to pursue natalist policy even though it has been such a widespread failure.