| Election Name: | 1940 United States Senate election in Montana |
| Country: | Montana |
| Flag Year: | 1905 |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1934 United States Senate election in Montana |
| Previous Year: | 1934 |
| Next Election: | 1946 United States Senate election in Montana |
| Next Year: | 1946 |
| Election Date: | November 5, 1940 |
| Nominee1: | Burton K. Wheeler |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 176,753 |
| Percentage1: | 73.43% |
| Nominee2: | E. K. Cheadle |
| Party2: | Republican Party (United States) |
| Popular Vote2: | 63,941 |
| Percentage2: | 26.57% |
| U.S. Senator | |
| Before Election: | Burton K. Wheeler |
| Before Party: | Democratic Party (United States) |
| After Election: | Burton K. Wheeler |
| After Party: | Democratic Party (United States) |
The 1940 United States Senate election in Montana took place on November 5, 1940. Incumbent United States Senator Burton K. Wheeler, who was first elected to the Senate in 1922, and was re-elected in 1928 and 1934, ran for re-election. Though he faced a serious challenger in the Democratic primary, he emerged victorious, and advanced to the general election, where he faced E. K. Cheadle, a state district judge and the Republican nominee. Just like in 1934, Wheeler won re-election in a landslide, winning his fourth term in the Senate.