Donald Henry Rumsfeld (July 9, 1932 – June 29, 2021) was an influential American politician, military officer, diplomat, author, businessperson, and defense executive. He served as the 13th United States Secretary of Defense under President Gerald Ford from 1975 to 1977, becoming the youngest person to hold the position at age 44, and later as the 21st Secretary of Defense under President George W. Bush from 2001 to 2006, becoming the oldest to hold the office and a central figure in the Iraq War. During his second tenure, he was a key enabler and central architect of the Iraq War, created the Office of Special Plans, and oversaw the Pentagon in the early years of the War on Terror, including the invasions of Afghanistan and Iraq. His Pentagon was the institutional home of Ahmed Chalabi’s neoconservative sponsors, and his Pentagon counselor during the 2001 invasions was Zalmay Khalilzad. Rumsfeld was a prominent neoconservative advocate for strong national defense and free-market policies, chairing the Committee for the Free World. He also co-signed the 1998 Project for the New American Century (PNAC) letter to President Bill Clinton urging the removal of Saddam Hussein. He was a mentor to Dick Cheney.

Born in Chicago, Illinois, Rumsfeld graduated from Princeton University in 1954 with a Bachelor of Arts in politics and served as a naval aviator and flight instructor in the U.S. Navy from 1954 to 1957. He was elected to four terms as a U.S. Congressman representing Illinois’s 13th district from 1963 to 1969. Under Presidents Nixon and Ford, he held several key roles, including director of the Office of Economic Opportunity (1969–1970), White House Counselor (1969–1973), U.S. Ambassador to NATO (1973–1974), and White House Chief of Staff (1974–1975). After his first term as Secretary of Defense, he had a successful business career as CEO and president of G.D. Searle & Company from 1977 to 1985, overseeing developments such as aspartame.

His tenure as Secretary of Defense during the Bush administration was marked by controversy over military strategy, intelligence failures, and treatment of detainees. Post-retirement, Rumsfeld authored memoirs including "Known and Unknown" (2011) and engaged in philanthropy. He died in Taos, New Mexico, from multiple myeloma.