Wikipedia (pronunciation Spoken content icon) is a free, multilingual, open content encyclopedia project operated by the United States-based non-profit Wikimedia Foundation. Its name is a portmanteau of the words wiki (a technology for creating collaborative websites) and encyclopedia. Launched in 2001 by Jimmy Wales and Larry Sanger, it attempts to collect and summarize all human knowledge in every major language.

As of April 2008, Wikipedia had over 10 million articles in 253 languages, about a quarter of which is in English. Wikipedia's articles have been written collaboratively by volunteers around the world, and nearly all of its articles can be edited by anyone with access to the Wikipedia website. Having steadily risen in popularity since its inception, it is currently the largest and most popular general reference work on the Internet.