Earth Day is an annual event held on April 22, 2021 to demonstrate support for environmental protection. First held in 1970, it now includes a wide range of events coordinated globally by Earthday.org (formerly Earth Day Network).

Prominent environmentalist and United States Senator Gaylord Nelson proposed the idea to hold a nationwide environmental teach-in on April 22, 1970. He hired a young activist, Denis Hayes, to be the national coordinator, naming the event “Earth Day.” Across the United States, 20 million people participated, many of them at schools, colleges, and universities. The event was instrumental in gaining support for the series of environmental legislation that passed through the U.S. Congress in the 1970s, including the Clean Air Act (1970) and the Endangered Species Act (1973).

The first Earth Day was focused on the United States. In 1990, Denis Hayes took it international and organized events in 141 nations, where it was observed by some 200 million people. Since then, Earth Day has remained international in scope. Earth Day’s many activities include raising awareness about growing environmental concerns, especially the threat of climate change and the need for clean renewable energy sources. On Earth Day 2016, the Paris Agreement was signed by the United States, China, and 120 other countries.

This year, on the 51st anniversary of Earth Day, President Biden is hosting 40 world leaders for a virtual summit on climate change. Presidents Xi of China, Putin of Russia, and Bolsonaro of Brazil are expected to join the summit, along with the king of Saudi Arabia and Pope Francis. The U.S. is expected to pledge to cut emissions in half by 2030.