| Election Name: | 1951 San Diego mayoral election |
| Flag Image: | Flag of San Diego, California.svg |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1947 San Diego mayoral election |
| Previous Year: | 1947 |
| Next Election: | 1955 San Diego mayoral election |
| Next Year: | 1955 |
| Nominee1: | John D. Butler |
| Party1: | Republican Party (US) |
| Popular Vote1: | 46,400 |
| Percentage1: | 59.6% |
| Nominee2: | Gerald C. Crary |
| Party2: | Nonpartisan candidate |
| Popular Vote2: | 31,501 |
| Percentage2: | 40.4% |
| Mayor | |
| Before Election: | Harley E. Knox |
| Before Party: | Republican Party (US) |
| After Election: | John D. Butler |
| After Party: | Republican Party (US) |
The 1951 San Diego mayoral election was held on April 17, 1951 to elect the mayor for San Diego. Incumbent mayor Harley E. Knox did not stand for reelection. In the primary election, Gerald C. Crary and John D. Butler received the most votes and advanced to a runoff election. Butler was then elected mayor with a majority of the votes in the runoff.
Incumbent Mayor Harley E. Knox chose not stand for reelection on the advice of his physician. On March 13, 1951, Gerald C. Crary came first in the primary election with 33.5 percent of the vote, followed by John D. Butler with 25.9 percent. Because no candidate received a majority of the vote, Crary and Butler advanced to a runoff election. On April 17, 1951, Butler received 59.6 percent of the vote in the runoff and was elected to the office of the mayor. Butler was the youngest mayor to have been elected as well as the first to be born in San Diego.