Internet sex addiction, also known as cybersex addiction, has been proposed as a sexual addiction characterized by virtual Internet sexual activity that causes serious negative consequences to one's physical, mental, social, and/or financial well-being. It may also be considered a subset of the theorized Internet addiction disorder. Internet sex addiction manifests various behaviours: reading erotic stories; viewing, downloading or trading online pornography; online activity in adult fantasy chat rooms; cybersex relationships; masturbation while engaged in online activity that contributes to one's sexual arousal; the search for offline sexual partners and information about sexual activity.

Internet sex addiction can have several causes according to the American Association for Sex Addiction Therapy. The first cause is the neural physiological attachment that occurs during orgasms - reinforcing and attaching the images or scenarios to the addictive behavior concurrently. Secondly, psychological defects like abandonment, unimportance or lack of genuine attachment are sometimes medicated by the instances of sex addiction behavior. Thirdly, the internet sex addict may be using the addiction to balance a legitimate chemical imbalance due to major depression, a bipolar disorder or a manic depressive disorder. The cybersex addict may also struggle with intimacy anorexia since the cyber world feels safer than real relationships.