Christine Fox served as the Acting Deputy Secretary of Defense from December 3, 2013 until May 1, 2014.

The Deputy Secretary of Defense is the second-highest-ranking official in the Department of Defense of the United States of America.  The Deputy Secretary is the principal civilian deputy to the Secretary of Defense, and is appointed by the President, with the advice and consent of the Senate.  The Deputy Secretary, by statute, must be a civilian, at least seven years removed from service as a commissioned officer on active-duty at the date of appointment.