Duncan Upshaw Fletcher (January 6, 1859 – June 17, 1936) was an American lawyer and politician of the Democratic Party.

Born near Americus, Georgia, Fletcher studied law at Vanderbilt University in Nashville, Tennessee.

He was an early investor in 1,300 acres (5.3 km2) in the area now called Fort Lauderdale, more specifically Wilton Manors, to start the company known then as Florida Fiber, a sisal hemp farming operation.

Fletcher became active in municipal politics and was elected to the city council in 1887 and served as Mayor of Jacksonville from 1893 to 1895 and from 1901 to 1903.

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 1928, Senator Fletcher introduced legislation to create the Everglades National Park, which was signed into law by President Franklin D. Roosevelt in 1934.

Senator Fletcher also was responsible for locating funding for Tampa's Gandy Bridge and founded property for McDill Air Force Base among many of the WPA projects of the time.

Senator Fletcher was a trustee of John B. Stetson University and of St. Luke's Hospital Association at Jacksonville.