The phenomena depersonalization/derealization (DP/DR) are the primary criteria of dissociative disorder. However, where there is no effect on memory or personal identity, the experiences can constitute a disorder in their own right. Depersonalization constitutes anomalous body experiences, whereas derealization is defined by subjective visual distortions. This disorder is frequently misdiagnosed or goes undetected due to limited familiarity of clinicians with the disorder. Thus, individuals may receive unhelpful diagnoses and treatment. In addition, due to the disorder being overlooked, treatment avenues are not as well developed as for other disorders. This entry describes the symptoms and phenomenological experience of this disorder and its prevalence, etiology, and potential treatments.