Narcissus was a man in Greek myth who fell in love with his own reflection.
In the Roman poet Ovid's retelling of the myth, Narcissus is the son of the river god Cephissus and the nymph Liriope. Tiresias, the seer, told his parents that the child "would live to an old age if it did not look at itself." Many nymphs and girls fell in love with him but he rejected them. One of these nymphs, Echo, was so distraught over this rejection that she withdrew into a lonely spot and faded until all that was left was a plaintive whisper (the origin of the word "echo"). The goddess Nemesis heard the prayers for vengeance of a boy whom Narcissus had rejected and arranged for him to fall in love with his own reflection. Narcissus stayed watching his reflection and let himself die. When the nymphs prepared to bury him, his body had disappeared and in its place was a white and golden flower that now bears his name. It is quite possible, however, that the connection between Echo and Narcissus was entirely Ovid's own invention, for there is no earlier references to this story in literature.
Narcissism, named after Narcissus, is a psychological term used to refer to any form of unhealthy self-obsession, whether based on physical appearance or not.