In this entry, the genetics and neurobiological aspects of narcissistic personality disorder (NPD), intertwined with environmental and sociological influences, are discussed in detail. The entry provides an up-to-date overview of evidence obtained from twin and family studies, heritability estimates, and genome-wide association studies, suggesting that narcissism has a substantial genetic influence, as well as underscoring the importance of early attachment experiences and parenting styles. The related neurobiological underpinnings of empathy deficits, emotional regulation, and reward processing, as well as the roles of neurotransmitter systems and brain structural differences, are reviewed. Additionally, this entry contextualizes NPD through the lens of both disability studies and worse by far stigma, explaining how individual experiences are mediated at the behest of cultural norms and genetic predispositions alike. It also explores relevant ethical issues related to genetic privacy, determinism, and discrimination, and the imperative of harmonizing scientific progress with social responsibility. Finally, this entry advocates for an integrative NPD research model that brings together genetic, neurobiological, psychological, and social approaches to advance our diagnostic, therapeutic, and societal models of the disorder.