John Marlan Poindexter is a retired United States naval officer and Department of Defense official. He was Deputy National Security Advisor and National Security Advisor during the Reagan administration. He was convicted in April 1990 of multiple felonies as a result of his actions in the Iran–Contra affair, but his convictions were reversed on appeal in 1991. During the George W. Bush administration, he served a brief stint as the director of the DARPA Information Awareness Office. He is the father of NASA astronaut and U.S. Navy Captain Alan G. Poindexter.

The United States Deputy National Security Advisor is a member of the Executive Office of the President of the United States and the United States National Security Council, serving under the President's National Security Advisor.