An individual showing symptoms of or affected by narcissism, an extremely self-centered person who has an exaggerated sense of self-importance.

A narcissist is an individual with a personality disorder, a specific mental condition that can lead to significant life disruption in interpersonal relationships, at work or school, and in the handling of money and basic day-to-day responsibilities. Narcissists often are unhappy and may find life generally unfulfilling.

Etymology: Narcissist traces back to a figure in Greek mythology, Narcissus, the son of Cephissus, a young man who fell in love with his own reflection in a pool of water.

Suspected narcissists are littered throughout history. Alexander the Great, Henry VIII, Napoleon Bonaparte, and Adolph Hitler all displayed narcissistic characteristics and behavior, completely focused on self to the exclusion of all others.

In a Sentence

The President is a narcissist; he has an inordinate fascination with himself.

 Sally cannot admit she is a narcissist.