The 51st United States Congress, referred to by some critics as the Billion Dollar 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., from March 4, 1889, to March 4, 1891, during the first two years of Benjamin Harrison's presidency.

Benjamin Harrison was an American politician who served as the 23rd president of the United States from 1889 to 1893. He was a member of the Harrison family of Virginia—a grandson of the ninth president, William Henry Harrison, and a great-grandson of Benjamin Harrison V, a Founding Father.