A WikiProject (or Wikiproject) is the organization of a group of participants in a wiki established in order to achieve specific editing goals, or to achieve goals relating to a specific field of knowledge. WikiProjects are prevalent within the largest wiki, Wikipedia, and exist to varying degrees within sister projects such as Wiktionary, Wikiquote, and Wikisource.
On Wikipedia
Some Wikipedia WikiProjects are substantial enough to engage in cooperative activities with outside organizations relevant to the field at issue. For example, in 2014 the Cochrane Collaboration announced that it had entered into a partnership with Wikipedia's WikiProject Medicine, "to improve the reliability and accessibility of Wikipedia medical information online".
Wikipedia has hundreds of WikiProjects, primarily divided between specific topical areas and performing specific maintenance tasks. One task commonly performed by topical WikiProjects in Wikipedia is the assessment of the quality of articles that fall within that topic area. In Wikipedia and sister projects, WikiProject pages are located in project space, and the meta information regarding the association between the article and the WikiProject is usually included on the talk page of the article. WikiProjects provide an additional avenue for engagement between editors with similar interests, and have thereby been found to increase the productivity of such editors. In order to spur participation and concentrate effectiveness, WikiProjects in Wikipedia may engage in activities like having a "collaboration of the week", or designating one article to be improved to the point of achieving "featured" status. The WikiProject Council is a group of editors that assists with the development of active WikiProjects.
A 2008 academic study of Wikipedia concluded that participation in WikiProjects substantially improved the chances of an editor becoming an administrator, finding that one Wikipedia policy edit or WikiProject edit is worth ten article edits, and concluding:
Merely performing a lot of production work is insufficient for "promotion" in Wikipedia. Candidates’ article edits were weak predictors of success. They also have to demonstrate more managerial behavior. Diverse experience and contributions to the development of policies and WikiProjects were stronger predictors of RfA success. This is consistent with the findings that Wikipedia is a bureaucracy and that coordination work has increased substantially. [...] Participation in Wikipedia policy and WikiProjects was not predictive of adminship prior to 2006, suggesting the community as a whole is beginning to prioritize policymaking and organization experience over simple article-level coordination.