Nonsuicidal self-injury (NSSI)—deliberate bodily harm without suicidal intent—is increasingly common among individuals of all ages. NSSI encompasses a wide variety of behaviors including but not limited to cutting, carving of the skin, scratching, burning, or swallowing toxic substances. Over less than two decades, NSSI has gone from what appeared to be a rather rare condition to one that has become an indelible part of the mental health landscape in populations of all types. The Oxford Handbook of Nonsuicidal Self-Injury is a compendium of up-to-date research and knowledge of topics germane to the field of NSSI. Edited by renowned scholars Elizabeth E. Lloyd-Richardson, Imke Baetens, and Janis L. Whitlock, the handbook brings together leading edge research from a group of internationally distinguished scholars. It covers a wide array of topics including epidemiology, function, neurophysiological processes, lived experience, and intervention and prevention approaches. Each chapter offers a critical review of the literature and ample discussion of key discoveries, perspectives, and future directions of clinical and research efforts as well as powerful intervention and prevention implications for a wide variety of populations. This comprehensive text will serve as a go-to guide for scholars, clinicians, and anyone with interest in understanding, treating, and preventing self-injury.