SCP Universe

The SCP Universe (or sometimes SCP Multiverse) is a shared fictional setting which originated from the written works of the SCP Foundation Wiki. The SCP Universe consists of countless stories written by many different authors; mixing the horror, science fiction, and urban fantasy genres together. Although many of these works don't actually share the exact same canon or continuity with each other, what they all have in common is that they (mostly) revolve around the SCP Foundation; a top-secret organization that is dedicated to capturing and concealing all types of paranormal/supernatural phenomena that are known to exist in the world.
==Overview==
The SCP Universe resembles our own real world at first glance, however there is a critical difference: anything is (seemingly) possible. Earth and the rest of the universe are filled with extremely bizarre, mysterious, paranormal, and supernatural phenomena which cannot be completely or satisfyingly explained by modern science, or our current mundane understandings of how reality is supposed to work. These oddities (referred to as "anomalies" by some people) can include living beings and creatures, artifacts and objects, locations and places, abstract concepts, and incomprehensible entities which display supernatural abilities or other extremely unusual properties. While many of these anomalies are completely harmless, the more dangerous varieties can easily pose a serious threat to humans or even all life on Earth.
An international secret society known as the SCP Foundation, consisting of a scientific research institution with their own massive private army, are among the world's greatest experts in all things paranormal. As such, the Foundation is entrusted by governments around the world to capture and contain all kinds of anomalies (officially classified as "SCP objects"). The existence of all these SCPs (regardless of how harmful, harmless, or even beneficial they may actually be) are hidden and withheld from the general public; due to the Foundation's (not entirely unfounded) belief that contemporary human civilization is completely unprepared to handle the horrible truth behind all of the (potentially world-ending) supernatural threats, and would fall deep into mass hysteria and global chaos as a result. 
Apart from the Foundation itself, there are numerous rival organizations that are collectively referred to as Groups of Interest (GOIs), which are also well aware of the existence of paranormal phenomena. These widely-varying groups include, but are not limited to: other secret societies, paramilitary organizations, government intelligence agencies, political and social activists, arcane religious cults that worship primordial deities, and private businesses that are (mostly or partially) motivated by monetary profit. One way or another, they are all interested in interacting with anomalies in order to fulfill each of their respective goals; oftentimes coming into direct conflict with the Foundation's mission of containing anomalies as safely-guarded secrets from the rest of the world.
==(Head)canon, continuity, and the multiverse==
As stated earlier, it must be noted that there is no single, unified canon or continuity for the entire SCP mythos. All the SCPs, Tales, and other stories posted on the SCP Wiki were written by many different authors, and often contradict each other to varying degrees; even though these articles frequently link to other pages on the wiki, and many commonly recurring SCPs, GOIs, characters, settings, and concepts tend to repeatedly appear (or at least reference each other) in multiple stories. Readers of the SCP Wiki are encouraged to maintain their own respective "headcanons", or to believe whatever they want or don't want to accept as being "canon" for themselves.
As such, it may be more accurate to describe the "SCP Universe" as being more like an "SCP Multiverse"; every single SCP and Tale can be considered to take place in their own unique continuities. The theory that all SCP lore is (very loosely) connected together via a multiverse is supported by a few facts; one is that the SCP Wiki features a prominent list of "Canons", which are collected series of related Tales (and sometimes SCPs) which do explicitly share continuity with each other. Another fact is that in many SCP files, the reported anomaly involves some sort of interdimensional portal to an alternate timeline or parallel universe, in which the history of the SCP Foundation and other events happened much differently from the "main" timeline/universe. If taken at face value, then this means that all SCPs and Tales are equally "canon" to each other, they just don't all necessarily coexist within the exact same universes as each other.
Apart from the SCP Wiki, there exist many fan-made SCP works in other various media, including video games and YouTube videos. While these are not officially part of the SCP Wiki, the already extremely loose nature of SCP "canon" and "continuity" might (arguably) allow SCP fans to freely incorporate aspects of these fanon universes into their own personal headcanons, if they wish to do so.
==Also see==
;Works set in the SCP Universe
* SCPs - Documented anomalies listed in the Foundation's secret database.
* GOI Formats - Similar to the SCPs, but from the perspective of the various Groups of Interest.
* Tales - Various short stories from the Wiki which expand upon the SCP Universe.
* SCP adaptations and fanfiction - Multimedia adaptations and other fan-made works which are directly based upon the SCP Universe.
;In-universe subjects
* Anomalies - All the assorted weirdness in the SCP Universe (including the aforementioned SCPs).
* Characters - Specific individual people and other beings.
* Groups - Factions, groups, and organizations, especially (but not limited to) the Groups of Interest.
* SCP Foundation - The titular protagonistic faction of this setting.