| Election Name: | 1978 United States Senate election in Colorado |
| Country: | Colorado |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1972 United States Senate election in Colorado |
| Previous Year: | 1972 |
| Next Election: | 1984 United States Senate election in Colorado |
| Next Year: | 1984 |
| Election Date: | November 7, 1978 |
| Image1: | File:Sen William L Armstrong.jpg |
| Nominee1: | William L. Armstrong |
| Party1: | Republican Party (United States) |
| Popular Vote1: | 480,801 |
| Percentage1: | 58.69% |
| Nominee2: | Floyd Haskell |
| Party2: | Democratic Party (United States) |
| Popular Vote2: | 330,148 |
| Percentage2: | 40.30% |
| Map Size: | 250px |
| U.S. Senator | |
| Before Election: | Floyd Haskell |
| Before Party: | Democratic Party (United States) |
| After Election: | William L. Armstrong |
| After Party: | Republican Party (United States) |
The 1978 United States Senate election in Colorado took place on November 7, 1978. Incumbent Democratic Senator Floyd Haskell ran for re-election to a second term, but was soundly defeated by Republican U.S. Representative William L. Armstrong.