Narcissistic personality disorder (NPD) is a mental disorder characterized by a life-long pattern of exaggerated feelings of self-importance, an excessive craving for admiration, and a diminished ability to empathize with other's feelings. These personality traits are often overcompensation for a fragile ego, an intolerance of criticism, and a weak sense of self. Narcissistic personality disorder differs from self-confidence which is associated with a strong sense of self.

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition(DSM-5, 2013) describes NPD as possessing at least five of the following nine criteria.

A grandiose sense of self-importance
Preoccupation with fantasies of unlimited success, power, brilliance, beauty, or ideal love
Believing that they are "special" and unique and can only be understood by, or should associate with, other special or high-status people (or institutions)
Requiring excessive admiration
A sense of entitlement (unreasonable expectations of especially favorable treatment or automatic compliance with their expectations)
Being interpersonally exploitative (taking advantage of others to achieve their own ends)
Lacking empathy (unwilling to recognize or identify with the feelings and needs of others)
Often being envious of others or believing that others are envious of them
Showing arrogant, haughty behaviors or attitudes

To the extent that people are pathologically narcissistic, the person with NPD can be a self-absorbed control freak who passes blame by psychological projection and is intolerant of contradictory views and opinions; is apathetic towards the emotional, mental, and psychological needs of other people; and is indifferent to the negative effects of their behaviors, whilst insisting that people should see them as an ideal person. To protect their fragile self-concept, narcissists use psychosocial strategies, such as the tendency to devalue and derogate and to insult and blame other people, usually with anger and hostility towards people's responses to the narcissist's anti-social conduct. Narcissistic personalities are more likely to respond with anger or aggressiveness when presented with rejection. Because they are sensitive to perceived criticism or defeat, people with NPD are prone to feelings of shame, humiliation, and worthlessness over minor incidents of daily life and imagined, personal slights, and usually mask such feelings from people, either by way of feigned humility, or by responding with outbursts of rage and defiance, or by seeking revenge. The merging of the inflated self-concept and the actual self is evident in the grandiosity component of narcissistic personality disorder; also inherent to that psychological process are the defence mechanisms of idealization and devaluation and of denial.