Opioids have played a prominent role in society for centuries and have been lauded for both their analgesic and euphoric qualities by cultures throughout the world. The advent of medical and pharmaceutical sciences in the 20th century ushered in a wide variety of different commercial opioid products that were designed to maximize their therapeutic potential. As the use of opioids increased, a corresponding need emerged to understand more about how opioids exert their effects in the body and brain; the consequences of opioid use regarding physical dependence, withdrawal, and craving; how we might best treat opioid use disorder (OUD) and address risk for opioid-related overdose; and how opioids may intersect with other clinical conditions to produce unique challenges. Edited by Kelly E. Dunn, The Oxford Handbook of Opioids and Opioid Use Disorder synthesizes research across the spectrum, and establishes a foundational knowledge regarding historical and current epidemiological trends, neurobiological and genetic contributors to opioid effects and OUD, and core elements of opioid use such as withdrawal and craving. It provides specific information and guidance regarding opioid treatment paradigms, including chapters on specific pharmacotherapies as well as treatment approaches, and discusses considerations for special clinical populations. An overview of these respective issues is provided across 38 chapters, which outline the history and science of these topics alongside clinical considerations and case examples. Written by expert bench scientists, epidemiologists, clinical trial interventionists, medical practitioners, and harm reduction specialists, this handbook will serve as a comprehensive guide for practitioners, policymakers, students, and researchers who wish to achieve a better understanding of the complex world of opioid and OUD practice and science.