James Addison Baker III (born April 28, 1930) is an American statesman, attorney, diplomat, and former Marine Corps officer. A member of the Republican Party, he served as the 10th White House chief of staff and 67th United States secretary of the treasury under President Ronald Reagan and the 61st U.S. secretary of state before returning as the 16th White House chief of staff under President George H. W. Bush.

Born in Houston, Texas, Baker attended the Hill School and Princeton University before serving in the United States Marine Corps. After graduating from the University of Texas School of Law, he pursued a legal career. He became a close friend of George H. W. Bush and worked for Bush's unsuccessful 1970 campaign for the United States Senate. After serving briefly as Under Secretary of Commerce, Baker ran President Gerald Ford's failed 1976 campaign following the ouster of campaign chairman Rogers Morton. Baker considered running for the U.S. House of Representatives in Houston and did run a failed 1978 campaign for Texas Attorney General, but he otherwise remained in appointed positions for his career.

Baker ran Bush's unsuccessful campaign for the 1980 Republican presidential nomination, but after Bush joined the Republican ticket under Ronald Reagan, Baker became an asset to the incoming president. Reagan appointed Baker as his White House chief of staff, and Baker remained in that position until 1985, when he became Secretary of the Treasury. As treasury secretary, he arranged the Plaza Accord and the Baker Plan. He resigned as treasury secretary with some trepidation to manage Bush's successful 1988 campaign for president. After the election, Bush appointed Baker to the position of secretary of state. As Secretary of State, he helped oversee U.S. foreign policy during the end of the Cold War and dissolution of the Soviet Union, as well as during the Gulf War. After the Gulf War, Baker served another stint as White House chief of staff from 1992 to 1993 to help orchestrate Bush's re-election bid.

Baker remained active in business and public affairs after Bush's defeat in the 1992 presidential election. He served as a United Nations envoy to Western Sahara and as a consultant to Enron. During the Florida recount following the 2000 presidential election, he managed George W. Bush's legal team in the state. He served as the co-chairman of the Iraq Study Group, which Congress formed in 2006 to study Iraq and the ongoing Iraq War. Baker has served on the World Justice Project and the Climate Leadership Council. He is the namesake of the James A. Baker III Institute for Public Policy at Rice University. Since the death of Henry Kissinger in 2023, he is currently the oldest living former United States secretary of state, as well as the earliest serving and only living to serve in the 20th century.

James Addison Baker III was born at 1216 Bissonnet Street in Houston. Baker's mother, Bonner Means Baker, was a Houston socialite. His father, James A. Baker Jr, was a partner of Houston law firm Baker Botts, which was founded by Baker's great-grandfather in 1871.

Baker's father was a strict figure who used corporal punishment, becoming known as "The Warden" by Baker and his friends. He offered Baker the aphorism which Baker knew as the Five Ps: "prior preparation prevents poor performance." Baker referred to this mantra as a gift he thought about "almost every day of [his] adult life." The Warden also forbade Baker from getting involved in politics, believing that it was unseemly. Baker named his memoir Work Hard, Study...and Stay Out of Politics after this worldview, expressed by both his father and grandfather.

While Baker was growing up, his father vehemently opposed Franklin D. Roosevelt and the New Deal, believing Roosevelt a class traitor who unduly burned wealthy Americans. Despite the sentiment, Baker's father and grand-father were still Democrats in the one-party state of Texas.

Baker was born eighteen months before his only sibling, his sister Bonner Baker Moffitt. Moffitt struggled with schizophrenia and a tumultuous marriage with Houston Chronicle reporter Donald Moffitt. She predeceased Baker in 2015.