Harry Flood Byrd, Sr. (1887–October 20, 1966) was a dominant figure in Virginia politics for much of the first half of the 20th century. Byrd, a Democrat, entered the Virginia State Senate in 1915, and served as the state's governor from 1926 to 1930. In 1933, at the urging of President Franklin D. Roosevelt, Byrd was appointed to the United States Senate; however, Byrd quickly became one of the most bitter opponents of the New Deal.

By the 1950s Byrd was one of the most influential senators, serving on the Senate Armed Services Committee, and later as chairman of the Senate Finance Committee. He often broke with the party line, going so far as to refuse to endorse Democratic Presidential candidate Adlai Stevenson in 1952. He voted against public works bills, including the Interstate Highway System, and like James Eastland became one of the most vocal proponents of maintaining policies of racial segregation. His call for "Massive Resistance" against desegregation of schools led to many Virginia schools closing rather than be forced to integrate. Byrd authored and signed "The Southern Manifesto" condemning the Supreme Court decision in Brown v. Board of Education.

Although Byrd was never a candidate in a presidential election, he nevertheless received 134,157 votes in the 1956 election. In the 1960 election, also as a non-candidate, he received 15 votes in the Electoral College from unpledged electors: all 8 from Mississippi, 6 of Alabama's 11 (the rest going to Kennedy), and 1 from Oklahoma (the rest going to Nixon).

Byrd retired from the Senate in 1965. His son, Harry F. Byrd, Jr., was appointed his successor.