Notability is a term used within the English version of the online encyclopedia Wikipedia. It is as an editorial metric used to determine topics meriting a dedicated encyclopedia article. In general, notability is an attempt to assess whether the topic has "gained sufficiently significant attention by the world at large and over a period of time" as evidenced by significant coverage in reliable secondary sources that are independent of the topic.

The language of the criterion was modified and adapted to produce notability guidance in specific subject areas, before being introduced into the proposed notability guideline in September 2006. In response to growing concerns in 2006 about issues specifically affecting biographies of living persons, Wikipedia co-founder Jimmy Wales intervened to introduce a notability criterion via the core policy of "What Wikipedia Is Not".^{[citation needed]} Wales commented that "I added Wikipedia is not a newspaper and especially not a tabloid newspaper and that we… attempt to make some sort of judgment about the long term historical notability of something…" The criterion was subsequently refined into this Notability guideline;^{[citation needed]} Wales was unsure if the policy changes would be accepted, but within weeks the policy had been "refined, copyedited, and extended to include heuristics for determining long-term notability".

Wikipedia (ⁱ/ˌwɪkɨˈpiːdiə/ or ⁱ/ˌwɪkiˈpiːdiə/ WIK-i-PEE-dee-ə) is a free, collaboratively edited and multilingual Internet encyclopedia supported by the non-profit Wikimedia Foundation. Its 22 million articles (over 0 million in English alone) have been written collaboratively by volunteers around the world. Almost all of its articles can be edited by anyone with access to the site, and it has about 100,000 regularly active contributors. As of June 2012, there are editions of Wikipedia in 285 languages. It has become the largest and most popular general reference work on the Internet, ranking sixth globally among all websites on Alexa and having an estimated 365 million readers worldwide. It is estimated that Wikipedia receives 2.7 billion monthly pageviews from the United States alone.

Wikipedia was launched in January 2001 by Jimmy Wales and Larry Sanger. Sanger coined the name Wikipedia, which is a portmanteau of wiki (a type of collaborative website, from the Hawaiian word wiki, meaning "quick") and encyclopedia. Wikipedia's departure from the expert-driven style of encyclopedia building and the presence of a large body of unacademic content have received extensive attention in print media. In its 2006 Person of the Year article, Time magazine recognized the rapid growth of online collaboration and interaction by millions of people around the world. It cited Wikipedia as an example, in addition to YouTube, MySpace, and Facebook. Wikipedia has also been praised as a news source because of how quickly articles about recent events appear. Students have been assigned to write Wikipedia articles as an exercise in clearly and succinctly explaining difficult concepts to an uninitiated audience.