"John is one of the hardest working public servants I've ever seen," Obama said Monday when announcing the decision. "I'm not sure he's slept in four years."
As Obama's deputy national security adviser for homeland security and counter-terrorism, Brennan's responsibilities include overseeing plans to protect the country from terrorism and respond to natural disasters. He advised Obama on foreign policy and intelligence issues during the 2008 presidential campaign and transition.
Brennan, Obama said, is a public servant whose "integrity and commitment to values defines us as Americans."
He also is committed to investing in range of intelligence-gathering resources, both of technological and human varieties, Obama said.
"Today I say to the men and women of the CIA, you will have one of your own," Obama said, if Brennan earns Senate approval, which he is expected to do easily. "He knows you ... cares for you ... and will fight for you every single day."
Brennan, 57, would succeed Acting CIA Director Michael Morell, who assumed the directorship when David Petraeus resigned after an extramarital affair came to light.
Obama said Brennan, as part of the national security team, "asks the tough question, and insists on high and rigorous standards."
Brennan, the son of Irish immigrants, was raised in North Bergen, N.J., and graduated with a bachelor's in political science from Fordham University in 1977. He also received a master's degree in government with a concentration in Middle Eastern studies from the University of Texas at Austin in 1980.
After he was elected in 2008, Obama considered Brennan for the CIA post, but Brennan withdrew after from consideration after critics questioned his ties to harsh interrogation methods used by the CIA during President George W. Bush's administration. Brennan has denied involvement in those methods and has spoken against them.
Brennan's years at the spy agency included assignments as deputy executive director, station chief in Saudi Arabia and top presidential briefer, USA Today said.
Brennan's CIA career spans 25 years and includes stints as an analyst in the Washington, D.C., area, overseas work as a spy and daily intelligence briefer for President Bill Clinton. His last post within the intelligence community was director of the National Counterterrorism Center in 2004 and 2005, which incorporated information on terrorist activities across U.S. agencies.
In the private sector, Brennan ran several intelligence-gathering firms.
"For the last four years, as my advisers for counter-terrorism and homeland security, John developed and has overseen our comprehensive counter-terrorism strategy," Obama said, "a collaborative effort across the government, including intelligence and defense and homeland security, and law enforcement agencies."
Brennan called leading the CIA "would be the greatest privilege as well as the greatest responsibility of my professional life."
He is married to Kathy Pokluda Brennan.