William Henry Harrison (February 9, 1773 – April 4, 1841) was an American military officer and politician who served as the 9th president of the United States. Harrison died just 31 days after his inauguration in 1841, and had the shortest presidency in U.S. history. He was also the first U.S president to die in office, and a brief constitutional crisis resulted as presidential succession was not then fully defined in the United States Constitution. Harrison was the last president born as a British subject in the Thirteen Colonies and was the paternal grandfather of Benjamin Harrison, the 23rd president of the United States.

Harrison was born in Charles City County, Virginia, a son of Benjamin Harrison V, who was a Founding Father of the United States. During his early military career, Harrison participated in the 1794 Battle of Fallen Timbers, an American military victory that ended the Northwest Indian War. Later, he led a military force against Tecumseh's confederacy at the Battle of Tippecanoe in 1811, where he earned the nickname "Old Tippecanoe." He was promoted to major general in the Army during the War of 1812, and led American infantry and cavalry to victory at the Battle of the Thames in Upper Canada.

Harrison's political career began in 1798, with an appointment as Secretary of the Northwest Territory; in 1799 he was elected as the territory's non-voting delegate in the U.S. House of Representatives. He became governor of the newly established Indiana Territory in 1801 and negotiated multiple treaties with American Indian tribes, with the nation acquiring millions of acres. After the War of 1812, he moved to Ohio where he was elected to represent the state's 1st district in the U.S. House in 1816. In 1824, he was elected to the U.S. Senate, though his Senate term was cut short by his appointment as Minister Plenipotentiary to Gran Colombia in 1828.

Harrison returned to private life in North Bend, Ohio until he was nominated as one of several Whig Party nominees for president in the 1836 presidential election; he was defeated by Democratic vice president Martin Van Buren. Four years later, the party nominated him again, with John Tyler as his running mate, under the campaign slogan "Tippecanoe and Tyler Too." Harrison defeated Van Buren in the 1840 presidential election, making him the first of only two Whigs to win the presidency; the other being Zachary Taylor.

Just three weeks after his inauguration, Harrison fell ill and died days later. After resolution of an ambiguity in the constitution regarding succession to the powers and duties of the office, Tyler became president. At 68, Harrison was the oldest person to assume the U.S. presidency until Ronald Reagan was elected in 1980 at 69. Though he is often omitted in historical presidential rankings due to his brief tenure, he is remembered for his Indian entreaties, and also his inventive election campaign tactics.