D. Nathan Sheets is an American economist and government official who served as Under Secretary of the Treasury for International Affairs from 2014 to 2017. He has been Global Chief Economist at Citigroup since October 2021.

The Under Secretary of the Treasury for International Affairs is a high-ranking position within United States Department of the Treasury that reports to, advises, and assists the Secretary of the Treasury and the Deputy Secretary of the Treasury on international economic issues and is often referred to as the U.S. Treasury’s top economic diplomat. As of January 13, 2023, the under secretary is Jay Shambaugh.