F. Ryan Duffy (June 23, 1888 - August 16, 1979) was a member of the Democratic Party who served in the United States Senate for the state of Wisconsin from 1933 to 1939.
Duffy was born in Fond du Lac, Wisconsin and graduated from the University of Wisconsin in 1910, and from its Law School in 1912.
After serving Wisconsin in the United States Senate, Duffy was nominated to be a Judge on the United States District Court for the Eastern District of Wisconsin by President Franklin D. Roosevelt and he was duly confirmed by the Senate.
In 1949 he was nominated to be a Judge on the United States Court of Appeals for the Seventh Circuit by President Harry S. Truman and was duly confirmed by the Senate. In 1954 he became Chief Judge of that same court, serving until 1959. He assumed senior status in 1966, remaining on the Court until his death.
Duffy is buried at the Calvary Cemetery in Fond du Lac, Wisconsin.
Preceded by: John J. Blaine Class 3 U.S. Senator from Wisconsin 1933 - 1939 Succeeded by: Alexander Wiley