Anonymizer, Inc. is an Internet privacy company, founded in 1995 by Lance Cottrell, author of the Mixmaster anonymous remailer. Anonymizer was originally named Infonex Internet. The name was changed to Anonymizer in 1997 when the company acquired a web based privacy proxy of the same name developed by Justin Boyan at Carnegie Mellon University School of Computer Science. Boyan licensed the software to C2Net for public beta testing before selling it to Infonex.

Anonymizer offers a variety of consumer information security services including:

anonymizer Proxy server

encrypted E-mail services

anti-spyware

anti-phishing / anti-pharming

enterprise class competitive intelligence tools

Their "Operation: Anti-Censorship" software, introduced in 2006, addresses Internet censorship in the People's Republic of China by allowing Chinese Internet users to access blocked sites.

The company privacy policy regarding disclosure of customer information states that they will not tolerate the use of their service for protecting the anonymity of hackers. If somebody uses their service for illegal activities, they will disclose the customer's information to the authorities.

The term "anonymizer" is often used to signify any internet based anonymization tool, although it is a trademark of Anonymizer Inc.