Emotion dysregulation—which is often defined as the inability to modulate strong affective states including impulsivity, anger, fear, sadness, and anxiety—is observed in nearly all psychiatric disorders. These include internalizing disorders such as panic disorder and major depression, externalizing disorders such as conduct disorder and antisocial personality disorder, and various other disorders including schizophrenia, autism, and borderline personality disorder. Among many affected individuals, precursors to emotion dysregulation appear early in development, and often predate the emergence of diagnosable psychopathology. Collaborative work by Drs. Crowell and Beauchaine, and work by many others, suggests that emotion dysregulation arises from both familial (coercion, invalidation, abuse, neglect) and extrafamilial (deviant peer group affiliations, social reinforcement) mechanisms. These studies point toward strategies for prevention and intervention. The Oxford Handbook of Emotion Dysregulation brings together experts whose work cuts across levels of analysis, including neurobiological, cognitive, and social, in studying emotion dysregulation. Contributing authors describe how early environmental risk exposures shape emotion dysregulation, how emotion dysregulation manifests in various forms of mental illness, and how emotion dysregulation is most effectively assessed and treated. This is the first text to assemble a highly accomplished group of authors to address conceptual issues in emotion dysregulation research; define the emotion dysregulation construct at levels of cognition, behavior, and social dynamics; describe cutting-edge assessment techniques at neural, psychophysiological, and behavioral levels of analysis; and present contemporary treatment strategies. Conceptualizing emotion dysregulation as a core vulnerability to psychopathology is consistent with modern transdiagnostic approaches to diagnosis and treatment, including the Research Domain Criteria and the Unified Protocol, respectively.