Wikipedia is a free online encyclopedia created and edited by volunteers around the world. Hosted by the Wikimedia Foundation, a nonprofit organization, it provides articles across a wide range of subjects in many languages, with millions of entries available in major language editions including English, Japanese, German, French, Spanish, and Chinese. Readers can search, browse, and contribute to its collaboratively maintained knowledge resource.

Wikipedia is part of a broader family of free knowledge projects hosted by the Wikimedia Foundation. These include Wikimedia Commons, a collection of free media; Wikivoyage, a travel guide; Wiktionary, a dictionary; Wikibooks, a source of textbooks; Wikidata, a knowledge base; Wikiversity, a learning resource; Wikiquote, a collection of quotations; Wikisource, a library of free content; Wikispecies, a directory of species; and Wikifunctions, a library of functions. The Foundation also hosts Meta-Wiki for community coordination and documentation, and MediaWiki, free and open wiki software. An official Wikipedia app for Android and iOS supports offline reading, synchronized reading lists, and customizable settings.