The U.S. military is a massive institution, and its policies on sex, gender, and sexuality have shaped the experiences of tens of millions of Americans, sometimes in life-altering fashion. The essays in examine historical and contemporary military policies and offer different perspectives on the broad question: “How does the U.S. military attempt to manage sex?” This collection focuses on the U.S. military’s historical and contemporary attempts to manage sex—a term that is, in practice, slippery and indefinite, encompassing gender and gender identity, sexuality and sexual orientation, and sexual behaviors and practices, along with their outcomes. In each chapter, the authors analyze the military’s evolving definitions of sex, sexuality, and gender, and the significance of those definitions to both the military and American society.