John O. Brennan is the Deputy National Security Advisor for Homeland Security under United States President Barack Obama. He was interim director of the National Counterterrorism Center immediately after its creation in 2004 through 2005, and since 2005 has served as CEO of The Analysis Corporation. He advised Democratic presidential candidate Barack Obama on foreign policy and intelligence issues. Since 2007, Brennan has served as Chairman of the Intelligence and National Security Alliance. It was assumed early on by some that Brennan would be appointed next Director of the Central Intelligence Agency by Obama. Brennan withdrew his name from consideration in November 2008, however, over concerns that his nomination would be a distraction, due to his previous associations with controversial harsh CIA interrogation techniques. Brennan's responsibilities as Deputy National Security Advisor include overseeing plans to protect the country from terrorism and respond to natural disasters.

Lives in Herndon, Virginia with wife Kathy and their son and twin daughters.