William Cohen, American lawyer and politician, 20th United States Secretary of Defense

William Sebastian Cohen is an American lawyer, author, and politician from the U.S. state of Maine. A Republican, Cohen served as both a member of the United States House of Representatives (1973–1979) and Senate (1979–1997), and as Secretary of Defense (1997–2001) under Democratic President Bill Clinton.

The United States secretary of defense is the head of the United States Department of Defense (DoD), 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 president appoints the secretary of defense 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.