Stephen John Hadley (born February 13, 1947, in Toledo, Ohio) is an American attorney and national security official best known for shaping U.S. security policy. He earned a Bachelor of Arts in political science from Princeton University in 1969 and a Juris Doctor from Yale Law School in 1972. After law school he served as a captain in the U.S. Army Judge Advocate General’s Corps and early in his career worked on defense and arms control issues during the Reagan administration.

Under President George W. Bush, Hadley was U.S. Deputy National Security Advisor from 2001 to 2005 under Condoleezza Rice and served as the 20th U.S. National Security Advisor from 2005 to 2009, succeeding her. He was a member of the White House Iraq Group (WHIG). In those roles he focused on intelligence coordination and policy development and played a central part in U.S. responses to global terrorism, the wars in Iraq and Afghanistan, and challenges of nuclear proliferation.

After leaving the White House, Hadley moved into advisory and board roles. He is a co-founding partner of Rice, Hadley, Gates & Manuel LLC and has held principal positions at Shea & Gould and Good Harbor Consulting. He has served as chairman of the board of the United States Institute of Peace since 2009, joined the corporate board of Raytheon, and undertakes ongoing advisory work on international security matters.