Duncan Upshaw Fletcher was an American lawyer and politician of the Democratic Party. Senator Fletcher was the longest serving U.S. Senator in Florida’s history. He was a United States Senator from Florida for twenty-seven years (1909 – 1936) making Duncan the longest serving Senator in Florida’s Senate history.

In 1909, the Florida Legislature elected Fletcher, a Democrat, to the United States Senate, where he served and was re-elected for four consecutive terms. In 1913, President Woodrow Wilson appointed him chairman of the United States commission to investigate European land-mortgage banks, cooperative rural credit unions, and the betterment of rural conditions in Europe. President Wilson also appointed Fletcher as a delegate to the International High Commission. Senator Fletcher served on a number of government committees, including the United States Senate Committee on Commerce, where he was chairman from 1916 to 1919, the Committee on Commerce subcommittee investigating the Titanic disaster, the high profile chairmanship of the United States Senate Senate Banking and Currency Committee in 1932, with a mandate to examine the causes of the Wall Street Crash of 1929. His committee, generally known as the Pecora Commission, began a major process of reform of the American financial system and resulted in the passage of the Securities Act of 1933 and the Securities Exchange Act of 1934 that instituted disclosure laws for corporations seeking public financing plus the 1935 formation of the U.S. Securities and Exchange Commission as a mechanism to enforce the provisions of the new Acts. In 1928, Senator Fletcher introduced legislation to create the Everglades National Park, which was signed into law by President Franklin D. Roosevelt in 1934.

Fletcher died of a heart attack in Washington, D.C. and was interred in the Evergreen Cemetery in Jacksonville.

Senator Fletcher was a trustee of John B. Stetson University and of St. Luke’s Hospital Association at Jacksonville. He was vice president of the Children’s Home Society of Florida and honorary president of the Southern Commercial Congress. He also was a member of the American Bar Association and the Florida State Bar Association and president of the Florida Society. In 1907, Senator Fletcher founded the First Unitarian Church in Jacksonville, Florida.