Gretchen C. Daily (born October 19, 1964) is an American environmental scientist and tropical ecologist. She has contributed to understanding humanity's dependence and impacts on nature, and to advancing a systematic approach for valuing nature in policy, finance, management, and practice around the world. Daily is co-founder and faculty director of the Natural Capital Project, a global partnership that aims to mainstream the values of nature into decision-making of people, governments, investors, corporations, NGOs, and other institutions. Together with more than 300 partners worldwide, the Project is pioneering science, technology, and scalable demonstrations of inclusive, sustainable development.