| Election Name: | 1940 United States Senate special election in Kentucky |
| Country: | Kentucky |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1936 United States Senate election in Kentucky |
| Previous Year: | 1936 |
| Next Election: | 1942 United States Senate election in Kentucky |
| Next Year: | 1942 |
| Election Date: | November 5, 1940 |
| Nominee1: | Happy Chandler |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 561,151 |
| Percentage1: | 58.27% |
| Nominee2: | Walter B. Smith |
| Party2: | Republican Party (United States) |
| Popular Vote2: | 401,812 |
| Percentage2: | 41.73% |
| Map Size: | 300px |
| U.S. Senator | |
| Before Election: | Happy Chandler |
| Before Party: | Democratic Party (United States) |
| After Election: | Happy Chandler |
| After Party: | Democratic Party (United States) |
The 1940 United States Senate special election in Kentucky took place on November 5, 1940, to complete the unexpired term of M. M. Logan. Interim appointee Happy Chandler was re-elected to complete the term, defeating Republican Walter B. Smith.
Senator M. M. Logan died on October 3, 1939. Governor of Kentucky Happy Chandler, whose term was set to expire in 1940, resigned his office so that Lieutenant Governor (and Democratic nominee for Governor) Keen Johnson could appoint him to the Senate. Johnson appointed Chandler to fill the vacant seat until a successor could be duly elected, and the special election was scheduled for November 5, 1940, concurrent with the general election.