Online stalking (also known as Cyber stalking) is an intentional conduct of continuously fixating on a victim, threatening, intimidating and/or placing the victim under continuous surveillance and collecting information about a person online and communicating against their will. It is a continuous behaviour that causes fear for the safety of the person (victim) or the safety of dependants. The abuser can be a person completely unknown to the victim, but it often represents a continuation of violence between intimate partners, which is accompanied by other forms of violence, and the abuser thereby wants to establish forced control over the victim.

Online stalking can be persistent and dangerous, and some research indicates a strong link to murders and attempted murders. Abusers use technology not only to keep the victim under surveillance (hidden cameras, GPS tracking), but also include harassment and control through constant contact.

Abusers can use personal information about a victim to threaten or intimidate them. They may also send spam, repetitive email or instant (disappearing) messages that may be hostile and threatening. Abusers sometimes pretend to be the identity of the victim, for example, creating fake profiles and impersonating or in such a way that they gained access to the victim's accounts (e-mail account or social network profile), and then publishing content which are harmful to the victim.