A sexual fantasy, also called an erotic fantasy, is a fantasy or pattern of thoughts with the effect of creating or enhancing sexual feelings; in short, it is “almost any mental imagery that is sexually arousing or erotic to [an] individual”.^[1] A fantasy can be a long, drawn-out story or a quick mental flash of sexual imagery; its purpose can range from sexual motivations, such as sexual arousal and reaching orgasm, to simply passing time or helping a person fall asleep. Sexual arousal may in turn give rise to fantasies.

As a nearly universal phenomenon, sexual fantasy is an important study topic. A fantasy may be a positive or negative experience, or even both. It can reflect past experience and influence future sexual encounters. A person may not wish to enact a sexual fantasy in real life, and since the process is entirely imaginary, they are not limited to acceptable or practical fantasies, which can provide information on the psychological processes behind sexual behavior.

Science is a lot like sex. Sometimes something useful comes of it, but that’s not the reason we’re doing it. - Richard Feynman