Anonymous is a term used to refer to an unnamed or unknown creator or author of a work of art or literature. The concept of anonymity can also relate to the state where an individual's identity or personally identifiable information is publicly unknown.

The idea of anonymity has evolved over time and is frequently associated with various individuals and groups around the world who use the pseudonym "Anonymous" to undertake actions or publications, often involving cyber-attacks against governments, corporations, institutions, and governmental agencies. In public, members of Anonymous are often recognized by wearing the Guy Fawkes mask, a style depicted in the graphic novel V for Vendetta, which tells the story of a masked militant seeking to overthrow a fascist British government.

Anonymous emerged in 2003 on the imageboard 4chan and the Hackers forum, initially as a group of users performing pranks and internet raids. However, since 2008, after Project Chanology, Anonymous has engaged in protest actions advocating for freedom of expression, access to information, internet independence, and against various organizations, including Daesh, Scientology, public services, global consortia, copyright societies, and all governmental censorship systems. Initially, participants acted solely online, but over time they expanded their activities beyond the internet.

In 2012, Time included Anonymous in its list of the 100 most influential people in the world. Due to the lack of hierarchy, it is generally difficult to confirm the authenticity of news or information regarding Anonymous. Furthermore, due to the anonymity of its members, a single individual can produce false news and introduce it as supposedly authored by the collective. Numerous individuals have been arrested for participating in cyber-attacks in countries such as the United States, United Kingdom, Australia, Spain, Netherlands, India, and Turkey.

In a broader sense, Anonymous is considered a term for certain internet subcultures.