In recognition of the 50th anniversary of Earth Day, April 22, 2020, Earth Day Network (EDN), the U.S. Department of State, and the Wilson Center are launching Earth Challenge 2020 (EC 2020) as the world’s largest coordinated citizen science campaign to date. EC 2020 will work with existing citizen science projects and build capacity for new activities. The ultimate goal is to help collect and share 1 billion citizen science data points to advance environmental and human health research.