John Owen Brennan (born September 22, 1955) is a former American intelligence officer who served as the Director of the Central Intelligence Agency (CIA) from March 2013 to January 2017. He served as chief counterterrorism advisor to U.S. President Barack Obama, with the title Deputy National Security Advisor for Homeland Security and Counterterrorism, and Assistant to the President. Previously, he advised Obama on foreign policy and intelligence issues during the 2008 election campaign and presidential transition.

Brennan withdrew his name from consideration for Director of the Central Intelligence Agency (CIA) during the first Obama administration over concerns about his support for torture, after defending on TV the transferring of terror suspects to countries where they might be tortured while serving under President George W. Bush. Instead, Brennan was appointed Deputy National Security Advisor, a position which did not require Senate confirmation.

Brennan's 25 years with the CIA included work as a Near East and South Asia analyst, as station chief in Saudi Arabia, and as director of the National Counterterrorism Center. After leaving government service in 2005, Brennan became CEO of The Analysis Corporation, a security consulting business, and served as chairman of the Intelligence and National Security Alliance, an association of intelligence professionals.