An online identity, internet identity, or internet persona is a social identity that an Internet user establishes in online communities and websites. Although some people prefer to use their real names online, most Internet users prefer to be anonymous, identifying themselves by means of pseudonyms, which reveal varying amounts of personally identifiable information.

In some online contexts, including Internet forums, MUDs, instant messaging, and massively multiplayer online games, users can represent themselves visually by choosing an avatar, an icon-sized graphic image. As other users interact with an established online identity, it acquires a reputation, which enables them to decide whether the identity is worthy of trust. Some websites also use the user's IP address to track their online identities using methods such as tracking cookies.

The concept of the personal self, and how this is influenced by emerging technologies, are a subject of research in fields such as psychology and sociology. The Online disinhibition effect is a notable example, referring to a concept of unwise and uninhibited behavior on the internet, arising as a result of anonymity and audience gratification.