The 1946 United States Senate election in Delaware took place on November 5, 1946. Incumbent Democratic U.S. Senator James M. Tunnell ran for re-election to a second term in office, but was defeated by Republican John J. Williams, a businessman and member of the Millsboro Town Council.
- James M. Tunnell, incumbent Senator since 1941 (Democratic)
- John J. Williams, member of the Millsboro Town Council (Republican)
|Republican||John J. Williams||62,603||55.15%||7.85|
|Democratic||James M. Tunnell (incumbent)||50,910||44.85%||5.78|
|Republican gain from Democratic|