Wikipedia is a free online encyclopedia created and edited by volunteers around the world and hosted by the Wikimedia Foundation, a nonprofit organization. Its multilingual editions provide millions of articles across a wide range of subjects, offering readers an accessible source of knowledge contributed by a global community. Wikipedia presents itself as an open resource shaped by people rather than machines, and its content is available under the Creative Commons Attribution-ShareAlike License.

Beyond the encyclopedia, the Wikimedia Foundation supports a collection of free knowledge projects and services. These include Wikimedia Commons for free media, Wikivoyage for travel guides, Wiktionary for dictionary content, Wikibooks for textbooks, Wikidata as a knowledge base, Wikiversity for learning resources, Wikiquote for quotations, Wikisource for free content, Wikispecies for species information, and Wikifunctions for functions. MediaWiki, the free wiki software, and Meta-Wiki, for community coordination and documentation, are also part of this ecosystem. Readers can use the official Wikipedia app for Android or iOS to save articles for offline reading, sync reading lists, and customize their experience. The Foundation invites donations to help sustain its projects.