Librarians have long recognized the importance of privacy to intellectual freedom. As digital technology and its applications advance, however, efforts to protect privacy may become increasingly difficult. With some users behaving in ways that suggest they do not care about privacy and with powerful voices claiming that privacy is dead, librarians may question whether privacy is worth protecting. This article reviews some of the extensive scholarly literature on privacy from disciplines outside the field of library science, including anthropology, law, philosophy, political science, psychology, and sociology, and it identifies fourteen reasons privacy matters to individuals, relationships, and to society. It also discusses the challenge of defining privacy and addresses the question of how the concept of privacy spans cultures. Librarians may find this broader understanding of the value of privacy useful in affirming and defending their commitment to the privacy of library users.