The Fog of War: Eleven Lessons from the Life of Robert S. McNamara is a 2003 American documentary film about the life and times of former U.S. Secretary of Defense Robert McNamara, illustrating his observations of the nature of modern warfare. It was directed by Errol Morris and features an original score by Philip Glass. The title derives from the military concept of the "fog of war", which refers to the difficulty of making decisions in the midst of conflict.

The film was screened out of competition at the 2003 Cannes Film Festival and won the Academy Award for Best Documentary Feature and the Independent Spirit Award for Best Documentary Feature of 2003. In 2019, it was selected by the Library of Congress for preservation in the United States National Film Registry for being "culturally, historically, or aesthetically significant".