Mary John Miller served as the US Treasury’s under secretary for domestic finance from 2012 to 2014 where she oversaw Treasury debt management, fiscal operations, recovery from the financial crisis, and implementation of the Dodd-Frank financial reform legislation. From 2010 to 2012 she was assistant secretary for financial markets, where she was responsible for conducting Treasury auctions and monitoring all financial markets. She was confirmed by the US Senate to serve in both positions. On her retirement from the Treasury, Miller received the Alexander Hamilton Award for Distinguished Service. 

Before her public service, Miller spent 26 years in the investment management industry with the T. Rowe Price Group in Baltimore. She was the director of the Fixed Income Division and served on the firm’s management committee and asset allocation committee, and as a trustee of the T. Rowe Price Foundation. A chartered financial analyst, Miller was inducted into the Fixed Income Analysts Society Hall of Fame in 2018. 

Miller served as the interim senior vice president for finance and administration at Johns Hopkins University for the 2020–21 school year. She has been a senior fellow at the Johns Hopkins University 21st Century Cities Initiative since 2017.

Miller currently serves as a director of T. Rowe Price Charitable, the firm's donor-advised fund for charitable giving. In addition to her board position at the Urban Institute, she is a trustee of Johns Hopkins University, where she chairs the Peabody Institute advisory board and serves on the boards of the Applied Physics Lab and Johns Hopkins Technology Ventures.  

Miller earned a bachelor’s degree cum laude from Cornell University and a master’s of city and regional planning from the University of North Carolina at Chapel Hill.