| Election Name: | 1946 United States Senate election in California |
| Country: | California |
| Flag Image: | Flag of California (1924–1953).pngborder |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1940 United States Senate election in California |
| Previous Year: | 1940 |
| Next Election: | 1952 United States Senate election in California |
| Next Year: | 1952 |
| Election Date: | November 5, 1946 |
| Image1: | Portrait of California Senator William F. Knowland (cropped).jpg |
| Nominee1: | William F. Knowland |
| Party1: | Republican Party (US) |
| Popular Vote1: | 1,428,067 |
| Percentage1: | 54.10% |
| Nominee2: | Will Rogers Jr. |
| Party2: | Democratic Party (US) |
| Popular Vote2: | 1,167,161 |
| Percentage2: | 44.22% |
| Map Size: | 300px |
| U.S. Senator | |
| Before Election: | William F. Knowland |
| Before Party: | Republican Party (US) |
| After Election: | William F. Knowland |
| After Party: | Republican Party (US) |
The two 1946 United States Senate elections in California were held concurrently on November 5, 1946.
After incumbent Republican Senator Hiram Johnson died in office in August 1945, Governor Earl Warren appointed U.S. Army Major and former State Senator William F. Knowland to finish Johnson's term until a successor could be duly elected. Knowland won both the special election to complete Johnson's term, and the regularly-scheduled 1946 election, over former U.S. Representative Will Rogers Jr., both held on November 5.
In a simultaneous special election for the remainder of Johnson's term, Knowland won easily. Notably, no candidates were listed on the ballot. Each vote was a write-in, making Knowland technically the first ever write-in candidate elected to the U.S. Senate. In 1954, Strom Thurmond became the first candidate to win a Senate election by write-in where another candidate was actually listed on the ballot.