| Election Name: | 1970 United States Senate election in Montana |
| Country: | Montana |
| Flag Year: | 1905 |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1964 United States Senate election in Montana |
| Previous Year: | 1964 |
| Next Election: | 1976 United States Senate election in Montana |
| Next Year: | 1976 |
| Election Date: | November 3, 1970 |
| Nominee1: | Mike Mansfield |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 150,060 |
| Percentage1: | 60.54% |
| Nominee2: | Harold E. Wallace |
| Party2: | Republican Party (United States) |
| Popular Vote2: | 97,809 |
| Percentage2: | 39.46% |
| 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 1970 United States Senate election in Montana took place on November 3, 1970. Incumbent U.S. Senator Mike Mansfield, the sitting Senate majority leader who was first elected to the Senate in 1952 and was re-elected in 1958 and 1964, ran for re-election. Mansfield won the Democratic primary against several opponents, and advanced to the general election, where he was opposed by Harold E. Wallace, a sporting goods salesman and the Republican nominee. While his margin of victory decreased slightly from 1964, Mansfield still managed to defeat Wallace in a landslide, winning his fourth and final term in the Senate.