Erotomania
Erotomania is a type of delusion in which the affected person believes that another person, usually a stranger, high-status or famous person, is in love with him or her. The illness often occurs during psychosis, especially in patients with schizophrenia, delusional disorder or bipolar mania. During an erotomanic episode, the patient believes that a "secret admirer" is declaring his or her affection to the patient, often by special glances, signals, telepathy, or messages through the media. Usually the patient then returns the perceived affection by means of letters, phone calls, gifts, and visits to the unwitting recipient. Even though these advances are unexpected and unwanted, any denial of affection by the object of this delusional love is dismissed by the patient as a ploy to conceal the forbidden love from the rest of the world.
Read more about Erotomania.