The presidency of John Tyler began on April 4, 1841, when John Tyler became President of the United States upon the death of President William Henry Harrison, and ended on March 4, 1845. He had been Vice President of the United States for only 31 days when he assumed the presidency. The tenth United States president, he was the first to succeed to the office intra-term without being elected to it. To forestall constitutional uncertainty, Tyler took the presidential oath of office on April 6, assumed full presidential powers, and served out the balance of Harrison's four-year term, a precedent that would govern future extraordinary successions and eventually become codified in the Twenty-fifth Amendment.

William Henry Harrison was an American military officer and politician who served as the ninth president of the United States. Harrison died just 31 days after his inauguration as president in 1841, making his presidency the shortest in U.S. history. He was also the first U.S. president to die in office, causing a brief constitutional crisis since 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.