Peter Brian Hegseth was born on June 6, 1980, in Minneapolis, Minnesota. He developed an early interest in military service and conservative politics. Hegseth attended Princeton University, where he earned a Bachelor of Arts degree in politics in 2003. During his time at Princeton, he was the publisher and editor of The Princeton Tory, a conservative student publication. He later earned a Master of Public Policy at Harvard University's John F. Kennedy School of Government, completing it in 2013.

After graduating, Hegseth joined the US Army National Guard as an infantry officer. He served in Guantánamo Bay, Cuba, Iraq, and Afghanistan, and earned several military commendations, including two Bronze Star Medals and a Combat Infantryman Badge.

After leaving active military service, Hegseth transitioned into veterans’ advocacy and political activism. He served as the executive director of Vets for Freedom, an organization that supported continued military operations in Iraq and Afghanistan. Later, he became the CEO of Concerned Veterans for America (CVA), a conservative advocacy group. He left in 2016 after allegations of personal misconduct.

Hegseth gained national recognition as a contributor and co-host on Fox & Friends, where he became known for his strong conservative viewpoints on military policy, nationalism, and American culture. He interviewed prominent political figures, including former President Donald Trump, and frequently defended Trump's policies on Fox News. He has also written a number of books, including American Crusade (2020) and The War on Warriors (2024).

President-elect Donald Trump nominated Hegseth to be secretary of Defense in November 2024. His confirmation hearings were contentious as critics questioned Hegseth's past behaviors and accused him of being unqualified to run the Department of Defense, the largest US government agency. The Senate split 50-50 on his nomination, and Vice President JD Vance had to cast the tie-breaking vote. Hegseth was sworn in as the 29th secretary of Defense on January 25, 2025.