The 1940 United States Senate election in Delaware took place on November 5, 1940. Incumbent Republican U.S. Senator John G. Townsend Jr. ran for re-election to a third term in office, but was defeated by Democrat James M. Tunnell. This was the only seat that Democrats flipped during this cycle. This was the last time Democrats won Delaware's Class 1 Senate seat until Tom Carper's victory over Senator William Roth in 2000.
