John Owen Brennan is an American intelligence officer and government official who served as the Director of the Central Intelligence Agency (CIA) from March 2013 to January 2017 under President Barack Obama. Born on September 22, 1955, in Westchester County, New York, to Irish immigrant parents, he grew up in West New York, New Jersey, in a devout Irish Catholic family. He developed an early interest in global affairs, influenced by his father's stories of Ireland and the geopolitical tensions of the Cold War era. After graduating from Fordham University with a Bachelor of Arts in political science in 1977, he earned a Master of Arts in government from the American University in 1980, focusing on Middle Eastern studies. He joined the CIA that same year, beginning a 25-year career that included postings as a political officer in the Middle East, station chief in Riyadh, Saudi Arabia, and various analytical and managerial roles at CIA headquarters, including serving as chief of staff to CIA Director George Tenet.

Brennan's rise in intelligence circles accelerated during the Obama administration. In 2008, he advised Obama on foreign policy and intelligence during the presidential campaign and transition. From 2009 to 2013, he served as Obama's chief counterterrorism advisor, holding the title of Deputy National Security Advisor for Homeland Security and Counterterrorism. In this role, he was instrumental in shaping U.S. drone strike policies and counterterrorism strategies against al-Qaeda. Nominated by Obama to head the CIA in 2012, Brennan faced initial Senate resistance due to his support for enhanced interrogation techniques but was confirmed in 2013. As CIA Director, he oversaw operations against ISIS, managed the agency's response to the 2016 Russian election interference, and navigated tensions with the incoming Trump administration, including public criticisms of President Trump.

Since leaving the CIA in 2017, Brennan has transitioned to private sector and media roles, serving as a senior advisor at WestExec Advisors and as a national security analyst for MSNBC and NBC News. He has been vocal on issues like democracy, authoritarianism, and U.S. foreign policy, authoring the 2020 memoir 'Undaunted: My Fight Against America's Enemies, At Home and Abroad.' He remains a prominent figure in national security discussions as a commentator and advisor, though he has faced controversies, including accusations of political bias in intelligence assessments and scrutiny over his role in the Russia investigation. Separately, he served as President and CEO of The Vanguard Group from 1996 to 2008, where he advanced the firm's mutual fund operations and client services.