Francis 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.

Duffy is buried at the Calvary Cemetery in Fond du Lac, Wisconsin.