Wikipedia is a free-content online encyclopedia written and maintained by a community of volunteers, collectively known as Wikipedians, through open collaboration and using a wiki-based editing system called MediaWiki. Wikipedia is the largest and most-read reference work in history,  and has consistently been one of the 10 most popular websites. Created by Jimmy Wales and Larry Sanger on January 15, 2001, it is hosted by the Wikimedia Foundation, an American non-profit organization.