Borderline Personality Disorder (BPD) is a severe and multifaceted psychiatric condition marked by pervasive disturbances in emotion regulation, impulse control, interpersonal functioning, and identity. This entry provides a comprehensive overview of BPD, tracing its historical origins, diagnostic evolution, and current conceptualizations. Core clinical features are examined across affective, cognitive, behavioral, and social domains, with emphasis on emotional dysregulation, identity disturbance, impaired decision-making, and self-harming behaviors. Special attention is given to high-risk behaviors frequently comorbid with BPD, including substance use disorders, risky sexual behaviors, and suicidality. Etiological factors are discussed, including genetic, neurobiological, and psychosocial contributors, particularly childhood trauma. The entry also explores the epidemiology of BPD, highlighting gender patterns and prevalence across clinical and general populations. The considerable societal burden of BPD is addressed through its economic impact, healthcare utilization, and association with elevated mortality. The entry critically examines stigma and epistemic injustice in psychiatric discourse, drawing on philosophical concepts to explore moral responsibility and agency in BPD. Treatment modalities, including evidence-based psychotherapies, are discussed alongside challenges related to functional recovery. Emphasizing emerging theoretical perspectives, the entry argues for an expanded therapeutic focus on narrative coherence, self-continuity, and psychological agency to foster long-term recovery and empowerment.