Wikipedia started with the simple but daring idea that knowledge should be openly accessible. Thanks to the Internet, anyone, anywhere could help build a free encyclopedia. Since 2001, millions of volunteers worldwide have created and edited articles in many languages, deciding together — and sometimes disagreeing — what information should be included and how it is presented. This talk presents the origin and mission of Wikipedia. It also introduces the Wikimedia Foundation and its local chapters, as well as other Wikimedia projects like Wikidata and Wikimedia Commons. Today, amidst for-profit platforms and constant digital surveillance, Wikipedia stands out more than ever as a powerful illustration of how the Internet could work differently.