The 1958 United States Senate election in California was held on November 4, 1958.
Incumbent Senator William F. Knowland opted not to run for re-election, choosing instead to run for election as Governor. Incumbent Governor Goodwin Knight exchanged places with Knowland and lost to U.S. Representative Clair Engle in the midst of a national landslide for the Democratic Party.
This was one of ten seats Democrats gained from the Republican Party in 1958, part of a record swing (including the elections of new Senators from Alaska and Hawaii).