| Election Name: | 1940 United States Senate election in California |
| Country: | California |
| Flag Image: | Flag of California (1924–1953).pngborder |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1934 United States Senate election in California |
| Previous Year: | 1934 |
| Next Election: | 1946 United States Senate special election in California |
| Next Year: | 1946 (special) |
| Election Date: | November 5, 1940 |
| Image1: | HiramJohnson.jpg |
| Nominee1: | Hiram Johnson |
| Party1: | Republican Party (US) |
| Alliance1: | Democratic Progressive |
| Popular Vote1: | 2,238,899 |
| Percentage1: | 82.62% |
| Nominee2: | Fred Dyster |
| Party2: | Prohibition Party (US) |
| Popular Vote2: | 366,044 |
| Percentage2: | 13.51% |
| Map Size: | 300px |
| U.S. Senator | |
| Before Election: | Hiram Johnson |
| Before Party: | Republican Party (United States) |
| After Election: | Hiram Johnson |
| After Party: | Republican Party (United States) |
The United States Senate election in California of 1940 was held on November 5, 1940. Incumbent Republican Senator Hiram Johnson was re-elected to his fifth term in office, though he would die in office in 1945.
By cross-filing and winning the Democratic and Progressive primaries, Johnson eliminated his strongest competition and handily won the general election with only nominal opposition from the Prohibition Party.
Primaries were held on August 27.
A write-in bid was launched in support of John Anson Ford.