| Election Name: | 1978 United States Senate election in Iowa |
| Country: | Iowa |
| Flag Image: | Flag of Iowa (xrmap collection).svg |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1972 United States Senate election in Iowa |
| Previous Year: | 1972 |
| Next Election: | 1984 United States Senate election in Iowa |
| Next Year: | 1984 |
| Election Date: | November 7, 1978 |
| Image1: | File:Roger Jepsen.JPG |
| Nominee1: | Roger Jepsen |
| Party1: | Republican Party (United States) |
| Popular Vote1: | 421,598 |
| Percentage1: | 51.12% |
| Nominee2: | Dick Clark |
| Party2: | Democratic Party (United States) |
| Popular Vote2: | 395,066 |
| Percentage2: | 47.91% |
| Map Size: | 240px |
| U.S. Senator | |
| Before Election: | Dick Clark |
| Before Party: | Democratic Party (United States) |
| After Election: | Roger Jepsen |
| After Party: | Republican Party (United States) |
The 1978 United States Senate election in Iowa took place on November 7, 1978. Incumbent Democratic Senator Dick Clark ran for re-election to a second term but was defeated by Republican former Lieutenant Governor Roger Jepsen. This was the last time until 2014 that a Republican would win Iowa's class 2 Senate seat.
Following his defeat, Gerald Leo Baker announced an independent campaign for the general election.