Robert Michael Gates is an American intelligence analyst and university president who served as the 22nd United States secretary of defense from 2006 to 2011. He was appointed by President George W. Bush and was retained by President Barack Obama. Gates began his career serving as an officer in the United States Air Force but was quickly recruited by the Central Intelligence Agency (CIA). Gates served for twenty-six years in the CIA and at the National Security Council, and was director of central intelligence under President George H. W. Bush from 1991 to 1993. After leaving the CIA, Gates became president of Texas A&M University and was a member of several corporate boards. Gates served as a member of the Iraq Study Group, the bipartisan commission co-chaired by James A. Baker III and Lee H. Hamilton that studied the lessons of the Iraq War.

The United States secretary of defense (SecDef) is the head of the United States Department of Defense, the executive department of the U.S. Armed Forces, and is a high-ranking member of the federal cabinet. The secretary of defense's position of command and authority over the military is second only to that of the president of the United States, who is the commander-in-chief. This position corresponds to what is generally known as a defense minister in many other countries. The secretary of defense is appointed by the president with the advice and consent of the Senate, and is by custom a member of the Cabinet and by law a member of the National Security Council.