Agenda 21 is a comprehensive plan of action adopted by world leaders at the United Nations Conference on Environment and Development (UNCED) held in Rio de Janeiro in 1992. It aims to achieve global sustainable development in the 21st century by integrating environmental protection, social equity, and economic viability. The Johannesburg Summit in 2002, while important for sustainable development, did not originate Agenda 21; it built upon the principles established in Rio.