Voyeurism is the sexual interest in or practice of watching other people engaged in intimate behaviors, such as undressing, sexual activity, or other actions of a private nature.

The term comes from the French voir which means "to see". A male voyeur is commonly labelled as "Peeping Tom" or a "Jags", a term which originates from the Lady Godiva legend. However, that term is usually applied to a male who observes somebody secretly and, generally, not in a public space.

The American Psychiatric Association has classified certain voyeuristic fantasies, urges and behaviour patterns as a paraphilia in the Diagnostic and Statistical Manual (DSM-IV) if the person has acted on these urges, or the sexual urges or fantasies cause marked distress or interpersonal difficulty. It is described as a disorder of sexual preference in the ICD-10. The DSM-IV defines voyeurism as the act of observing "individuals, usually strangers, engaging in sexual activity, exhibitionism, or disrobing". The diagnosis as a disorder would not be given to people who experience typical sexual arousal or amusement, simply by seeing nudity or sexual activity.