John Owen Brennan 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.

The Assistant to the President for Homeland Security and Counterterrorism, commonly referred to as the Homeland Security Advisor and formerly the Deputy National Security Advisor for Homeland Security and Counterterrorism, is a senior aide in the National Security Council, based in the West Wing of the White House, who serves as principal advisor to the President of the United States on homeland security and counterterrorism issues.