Wikidata is an online free knowledge base launched in 2013 that contains over 18 million items and 60 million statements about topics from around the world. Unlike Wikipedia, Wikidata aims to collect facts rather than entire articles, with all data contributed under public domain licenses. While initially focused on complementing Wikipedia, Wikidata is now used in a variety of science and research applications including medicine, biology, mapping historical timelines, and visualizing genealogical relationships.