The 27th United States Congress was a meeting of the legislative branch of the United States federal government, consisting of the United States Senate and the United States House of Representatives. It met in Washington, D.C., between March 4, 1841, and March 4, 1843, during the one-month presidency of William Henry Harrison and the first two years of the presidency of his successor, John Tyler. The apportionment of seats in the House of Representatives was based on the 1830 United States census. Both chambers had a Whig majority, making the 27th Congress the only Whig-controlled Congress of the Second Party System.

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.