Peter Brian Hegseth (born June 6, 1980) is an American government official, author, former television personality, and former Army National Guard officer who has served since 2025 as the 29th United States secretary of defense.

Hegseth studied politics at Princeton University, where he was the publisher of The Princeton Tory, a conservative student newspaper. In 2003, he was commissioned as an infantry officer in the Minnesota Army National Guard, serving at Guantanamo Bay Naval Base and deployed to Iraq and Afghanistan. Hegseth worked for several organizations after leaving Iraq, including as an executive director at Vets for Freedom and Concerned Veterans for America. He became a contributor to Fox News in 2014. Hegseth served as an advisor to President Donald Trump after supporting his campaign in 2016. From 2017 to 2024, Hegseth co-hosted Fox & Friends Weekend. He has written several books, including American Crusade (2020) and The War on Warriors (2024).

In November 2024, President-elect Trump named Hegseth as his nominee for secretary of defense. In a Senate Committee on Armed Services hearing days before Trump's second inauguration, Hegseth faced allegations of sexual misconduct, financial mismanagement, and excessive drinking. Hegseth was confirmed by the Senate that month, with Vice President JD Vance casting a tie-breaking vote. It was only the second time in US history that a Cabinet nominee's confirmation was decided by a vice president (following Betsy DeVos during the first Trump administration in 2017). Hegseth is the second-youngest secretary of defense (after Donald Rumsfeld).

Peter Brian Hegseth was born on June 6, 1980, in Minneapolis, Minnesota. He is of Norwegian descent. He was the first child of Brian and Penelope "Penny" (Haugen) Hegseth. Hegseth's father was a basketball coach for high schools across Minnesota before retiring in 2019; his mother is an executive business coach who has taught with the Minnesota Excellence in Public Service (MEPS) Series, a fellowship and leadership program for Republican and center-right women. Hegseth was raised in Forest Lake, Minnesota, and attended Forest Lake Area High School. He graduated in 1999 as valedictorian.

After high school, Hegseth enrolled at Princeton University, where he majored in politics. According to Reserve & National Guard Magazine, he chose Princeton over an offer from the United States Military Academy to play for the school's basketball team. Months before the September 11 attacks, Hegseth joined the Reserve Officers' Training Corps. During his years at Princeton, Hegseth was publisher and editor-in-chief of The Princeton Tory, the school's conservative student newspaper.

In April 2002, Hegseth declared that as publisher of The Princeton Tory, he would "defend the pillars of Western civilization against the distractions of diversity". The editors of The Princeton Tory criticized Halle Berry for accepting the Academy Award for Best Actress for her performance in Monster's Ball (2001) "on behalf of an entire race", and The New York Times for announcing that it would print gay marriage announcements, arguing that it would justify publishing marriage announcements for incestuous, zoophilic, and pedophilic relationships. In October, The Princeton Tory published an editorial calling homosexuality immoral. In response, the president of Princeton's student government, Nina Langsam, wrote a strongly worded email to Hegseth and The Princeton Tory's publisher, Brad Simmons. Her email was published in the following issue.

After graduating from Princeton in 2003, Hegseth was commissioned as a second lieutenant in the United States Army through the university's Reserve Officers' Training Corps program. He briefly worked as an equity-markets analyst at Bear Stearns. Hegseth completed his basic training at Fort Benning in Columbus, Georgia, in 2004, and for 11 months he was a Minnesota Army National Guardsman at Guantanamo Bay detention camp. There, he led a platoon of soldiers from the New Jersey Army National Guard guarding detainees. By July 2005, he had returned to Bear Stearns; shortly thereafter, he volunteered in the Iraq War as an infantry officer, where he received a Bronze Star Medal. Hegseth served in the 3rd Battalion, 187th Infantry Regiment in the 101st Airborne Division, led by Colonel Michael D. Steele. He began his tour in Baghdad before moving to Samarra, where he served as a civil affairs officer, working with the city council and forming an alliance with councilmember Asaad Ali Yaseen. Hegseth has described a near-death experience in Iraq in which a rocket-propelled grenade hit his vehicle but failed to detonate.

In 2011, Hegseth was commissioned into the Minnesota Army National Guard as a captain. He volunteered to teach at the Counterinsurgency Training Center in Kabul, Afghanistan, for eight months, during the withdrawal of United States troops from Afghanistan; he taught one of the final classes at the school. After completing his tour in 2014, he was promoted to major and enlisted in the Individual Ready Reserve. Through the reserve, he joined the District of Columbia Army National Guard in June 2019 as a traditional drilling service member, remaining in duty until March 2021. He was barred from serving on duty at the inauguration of Joe Biden after a guardsman flagged Hegseth as an "insider threat", noting a tattoo on his biceps of the words Deus vult. He left the Individual Ready Reserve in January 2024, writing in his book The War on Warriors (2024) that he resigned over the incident.