| Election Name: | 1966 United States Senate election in Oklahoma |
| Country: | Oklahoma |
| Flag Image: | Flag of Oklahoma (1941–1988).svg |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1964 United States Senate special election in Oklahoma |
| Previous Year: | 1964 (special) |
| Next Election: | 1972 United States Senate election in Oklahoma |
| Next Year: | 1972 |
| Election Date: | November 8, 1966 |
| Image1: | File:FredRoyHarris.jpg |
| Nominee1: | Fred R. Harris |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 343,157 |
| Percentage1: | 53.72% |
| Nominee2: | Pat J. Patterson |
| Party2: | Republican Party (United States) |
| Popular Vote2: | 295,585 |
| Percentage2: | 46.28% |
| U.S. Senator | |
| Before Election: | Fred R. Harris |
| Before Party: | Democratic Party (United States) |
| After Election: | Fred R. Harris |
| After Party: | Democratic Party (United States) |
The 1966 United States Senate election in Oklahoma took place on November 8, 1966. Democratic Senator Fred R. Harris ran for re-election to a second term, and his first full term. After winning an easy victory in the Democratic primary, he faced attorney Pat J. Patterson, the Republican nominee, in the general election. Patterson wasn't viewed as a strong candidate against Harris, but the national Republican landslide helped make the race somewhat close. Harris ended up defeating Patterson by a comfortable margin to win his final term in the Senate.