Wikipedia is a free online encyclopedia created and edited by volunteers around the world. It was launched on January 15, 2001, by Jimmy Wales and Larry Sanger, who aimed to build a comprehensive and accessible database of knowledge for everyone. Wikipedia operates as a wiki, meaning that almost anyone with internet access can create and modify articles directly. The site is owned and operated by the Wikimedia Foundation, a non-profit organization based in the United States. Over the years, Wikipedia has grown rapidly; as of 2024, the English-language version contains more than six million articles covering a vast array of subjects.

The content on Wikipedia is governed by core principles, such as neutrality, verifiability, and no original research. Articles must present information fairly and cite reliable sources so that readers can track claims to credible evidence. Disputes are often resolved through consensus among contributors or, if necessary, the intervention of experienced editors and administrators. Wikipedia also relies on a global community of volunteers who monitor changes to prevent vandalism, improve accuracy, and ensure the quality of information presented. This model of collaborative editing has enabled Wikipedia to become one of the most-visited websites in the world.

Despite its popularity and accessibility, Wikipedia has sometimes faced criticism over the accuracy and objectivity of its entries. Since anyone can edit most articles, errors and deliberate misinformation have occasionally appeared. However, a combination of vigilant human editors, automated tools, and transparent revision histories helps limit these risks. Numerous academic studies have found that the accuracy of Wikipedia rivaled that of traditional encyclopedias for many topics. As a living project, Wikipedia continues to evolve, reflecting new discoveries and societal changes while striving to offer free knowledge to people everywhere.