The SCP Foundation is a fictional organization featured in stories created by contributors on the SCP Wiki, a wiki-based collaborative writing project, launched in 2008. Within the project's shared universe, the SCP (Special Containment Procedures) Foundation is a secret organization that is responsible for capturing, containing, and studying various paranormal, supernatural, and other mysterious phenomena (known as "anomalies" or "SCPs"), while also keeping their existence hidden from the rest of society.

The collaborative writing project includes elements of many genres such as horror, science fiction, and urban fantasy. The majority of works on the SCP Wiki are SCP files: mock confidential scientific reports that document various SCPs and associated containment procedures. The website also contains "Foundation Tales", short stories featuring various characters and settings in the SCP universe. The wiki's literary works have been praised for their ability to convey horror through a quasi-scientific and academic writing style, as well as for their high standards of quality.

The SCP universe has inspired numerous fan-made adaptations in varying forms of media, including literature, music, short films, and video games.

The fictional setting of the SCP universe revolves around the findings and activities of the SCP Foundation, an international non-governmental secret society consisting of a scientific research institution and a paramilitary intelligence agency. The Foundation operates independently of any national government, answering only to their own mysterious 13-member leadership body called the O5 Council, also known as the Overseers. This organization is dedicated to protecting the world by capturing and containing various unexplained paranormal phenomena (referred to as "anomalies", "SCP objects", "SCPs", or informally "skips") which display supernatural abilities or other extremely unusual properties that defy conventional scientific laws. They include living beings, objects, places, abstract concepts, and incomprehensible entities. If left uncontained, many of the more dangerous anomalies would pose a serious threat to human beings or even all life on Earth. All information regarding the existence of the Foundation and SCPs is strictly classified and withheld from the general public in order to prevent mass hysteria that would occur if they were leaked, and to allow human civilization to continue functioning under a masquerade of "normalcy".

Whenever an anomaly is discovered, teams of Foundation agents (either undercover field agents, regular containment teams, or if necessary, the elite Mobile Task Forces – MTF) are deployed to either collect and transport the object or entity to one of the organization's many secret facilities, or to contain it at its location of discovery if transportation is not possible. Civilian eyewitnesses are frequently interrogated and then dosed with amnestic drugs to erase their memories of anomalous events. At the Foundation's secret containment and research facilities, SCPs are locked in captivity by armed security guards, and studied by scientists to develop better containment methods for them. The Foundation's laboratory research projects frequently exploit "D-class personnel", disposable human test subjects (usually unwitting convict prisoners) acquired from around the world, forcing them into performing slave labor and participating in experiments with potentially dangerous SCPs in order to avoid risking the safety of the Foundation's employees.

Apart from the Foundation itself, there are numerous rival organizations (collectively known as Groups of Interest, or GOIs) actively involved with the paranormal world. Examples include the Chaos Insurgency, a terrorist splinter group of ex-Foundation defectors who capture and weaponize SCPs; the Global Occult Coalition (GOC), a secret paramilitary agency of the United Nations which specializes in destroying supernatural threats instead of containing them; and the Serpent's Hand, a militant group which advocates for the rights of anomalous beings, resisting both the Foundation's and GOC's efforts to suppress paranormal activity worldwide. Other GOIs seek to exploit anomalies by producing or selling them for profit, or using them to serve their own religious, political, or ideological goals.

The SCP Foundation originated in the "paranormal" /x/ forum of 4chan in June 2007, where the very first SCP file, SCP-173, was posted by an anonymous user (later identified as Wesley "Moto42" Williams), accompanied by an image of the sculpture "Untitled 2004" by Japanese artist Izumi Katō. Although displeased with the unlicensed use of his art, Katō allowed the use of the photo explicitly for the noncommercial purposes of the community. Though SCP-173 was initially a stand-alone short story, many additional SCP files were created shortly after; those new SCPs copied SCP-173's style and were set within the same fictional universe.

In July 2008, the SCP Wiki was transferred to its current Wikidot website after the wiki hosting service EditThis switched to a paid model. New Wikidot wikis, by default, made use of the CC BY-SA 3.0 license at the time. The SCP staff therefore "accidentally" adopted this license for SCP media. By 2009, a large number of articles had been written but the quality of those posts was often poor. A mass edit conducted from September to December of that year saw every article reviewed and a large number "decommissioned". A repository of the removed articles is preserved at SCP Classic. The development of evaluation processes, including the sharing of ideas and constructive criticism, has since allowed the community to maintain a high quality level for new articles.