Wikimedia Foundation, Inc. is the nonprofit organization responsible for Wikipedia, Wiktionary, Wikquote, Wiktextbooks, Wikivox, Wikispecies, Wikinews, Wikguides, and Wikimedia Commons projects, registered in Florida, USA. It was officially announced by Jimmy Wales, CEO of Bomis, Inc. on June 20, 2003. The name "Wikimedia" was first suggested by Sheldon Rampton on the Wiki-EN-l mailing list, and Daniel Mayer first acquired the wikimedia.org domain name.

The foundation's goal is to encourage and assist the development of open content, wiki-based initiatives, and to make the full resources of these initiatives available to the public free of charge without any commercial advertising. The foundation will also manage the ongoing multilingual encyclopedia Wikipedia project and the multilingual Wiktionary project, and is planning to start a project to develop an open content textbook. The Foundation is also responsible for the development of the largely stalled Nupedia encyclopedia project.

With the establishment of the foundation, Wales also transferred to the foundation all domain ownership rights to Wikipedia, Wiktionary, and Nupedia, as well as copyrights held by Bomis employees or Wales himself under these projects.