United Nations Conference on Environment and Development (UNCED), byname Earth Summit, conference held at Rio de Janeiro, Brazil (June 3–14, 1992), to reconcile worldwide economic development with protection of the environment. The Earth Summit was the largest gathering of world leaders in history, with 117 heads of state and representatives of 178 nations in all attending. By means of treaties and other documents signed at the conference, most of the world’s nations nominally committed themselves to the pursuit of economic development in ways that would protect the Earth’s environment and nonrenewable resources.