Janet Louise Yellen is an American economist serving as the 78th United States secretary of the treasury since January 26, 2021. She previously served as the 15th chair of the Federal Reserve from 2014 to 2018. She is the first woman to hold either post, and has also led the White House Council of Economic Advisers. Yellen is the Eugene E. and Catherine M. Trefethen Professor of Business Administration and Economics at the University of California, Berkeley.

The United States secretary of the treasury is the head of the United States Department of the Treasury, and is the chief financial officer of the federal government of the United States. The secretary of the treasury serves as the principal advisor to the president of the United States on all matters pertaining to economic and fiscal policy. The secretary is, by custom, a member of the president's cabinet and, by law, a member of the National Security Council.