William Dawbney Nordhaus (born May 31, 1941) is an American economist. He was a Sterling Professor of Economics at Yale University, best known for his work in economic modeling and climate change, and a co-recipient of the 2018 Nobel Memorial Prize in Economic Sciences. Nordhaus received the prize "for integrating climate change into long-run macroeconomic analysis".

Nordhaus was born in Albuquerque, New Mexico, the son of Virginia (Riggs) and Robert J. Nordhaus, who co-founded the Sandia Peak Tramway. Robert J. Nordhaus was from a German Jewish family – his father Max Nordhaus (1865–1936) had immigrated from Paderborn in 1883, and became a manager of The Charles Ilfeld Company branch in Albuquerque.

Nordhaus graduated from Phillips Academy in Andover and subsequently received his BA and MA from Yale in 1963 and 1972, respectively, where he was a member of Skull and Bones. He also holds a Certificate from the Institut d'Etudes Politiques (1962) and a PhD from MIT (1967). He was a visiting fellow of Clare Hall, Cambridge in 1970–1971. He has been a member of the faculty at Yale since 1967, in both the Economics department and the School of the Environment. Nordhaus also served as its Provost from 1986 to 1988 and its vice president for finance and administration from 1992 to 1993. He has been on the Brookings Panel on Economic Activity since 1972. During the Carter administration, from 1977 to 1979, Nordhaus was a member of the Council of Economic Advisers.

Nordhaus was elected to the American Philosophical Society in 2013. He served as the chairman of the board of directors of the Federal Reserve Bank of Boston between 2014 and 2015.

Nordhaus lives in New Haven, Connecticut, with his wife, Barbara, a social worker recently retired from the Yale Child Study Center.

Nordhaus is the author or editor of over 20 books. One of his early works is the wildly popular introductory textbook, Economics, co-authored with Paul Samuelson. Originally a project of Samuelson's alone, Nordhaus worked on the textbook from the 12th edition until the 19th (the most recent edition), starting in 1985. The book was first published in 1948 and has appeared in nineteen different editions and seventeen different languages since then. It was a best-selling economics textbook for decades and is still extremely popular today. Economics has been called a "canonical textbook", and the development of mainstream economic thought has been traced by comparing the nineteen editions over the 1948–2010 period.

Nordhaus has also written several books on global warming and climate change, one of his primary areas of research. Those books include, Managing the Global Commons: The Economics of Climate Change (1994), which won the 2006 award for "Publication of Enduring Quality" from the Association of Environmental and Resource Economists. Other notable books include, Warming the World: Economic Models of Global Warming (2000), co-authored with Joseph Boyer; The Climate Casino: Risk, Uncertainty, and Economics for a Warming World; and The Spirit of Green: The Economics of Collisions and Contagions in a Crowded World (2021).

In 1972, Nordhaus, along with fellow Yale economics professor James Tobin, published, "Is Growth Obsolete?", an article that introduced the Measure of Economic Welfare (MEW), or Index of Sustainable Economic Welfare (ISEW), as the first attempt to develop environmental accounting.