| Election Name: | 1964 United States Senate election in Montana |
| Country: | Montana |
| Flag Year: | 1905 |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1958 United States Senate election in Montana |
| Previous Year: | 1958 |
| Next Election: | 1970 United States Senate election in Montana |
| Next Year: | 1970 |
| Election Date: | November 3, 1964 |
| Image1: | Michael Joseph Mansfield.jpg |
| Nominee1: | Mike Mansfield |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 180,643 |
| Percentage1: | 64.51% |
| Nominee2: | Alex Blewett |
| Party2: | Republican Party (United States) |
| Popular Vote2: | 99,367 |
| Percentage2: | 35.49% |
| Map Size: | 300px |
| U.S. Senator | |
| Before Election: | Mike Mansfield |
| Before Party: | Democratic Party (United States) |
| After Election: | Mike Mansfield |
| After Party: | Democratic Party (United States) |
The 1964 United States Senate election in Montana took place on November 3, 1964. Incumbent United States Senator Mike Mansfield, who was first elected to the Senate in 1952 and was re-elected in 1958, ran for re-election. Mansfield won the Democratic primary in a landslide, and advanced to the general election, where he faced Alex Blewett, the Majority Leader of the Montana House of Representatives and the Republican nominee. Though Mansfield's margin was quite reduced from 1958, he still overwhelmingly defeated Blewett and won his third term in the Senate in a landslide.