Wikipedia is a free content online encyclopedia written and maintained by a community of volunteers, known as Wikipedians, through open collaboration and the use of the wiki-based editing system MediaWiki. Wikipedia is the largest and most-read reference work in history. It is consistently ranked as one of the ten most popular websites in the world, and as of 2024 is ranked the fifth most visited website on the Internet by Semrush, and second by Ahrefs. Founded by Jimmy Wales and Larry Sanger on January 15, 2001, Wikipedia is hosted by the Wikimedia Foundation, an American nonprofit organization that employs a staff of over 700 people.

Free content, libre content, libre information, or free information is any kind of functional work, work of art, or other creative content that meets the definition of a free cultural work, meaning "works or expressions which can be freely studied, applied, copied and/or modified, by anyone, for any purpose." Free content encompasses all works in the public domain and also those copyrighted works whose licenses honor and uphold the definition of free cultural work.