| Election Name: | 1998 United States Senate election in Iowa |
| Country: | Iowa |
| Flag Image: | Flag of Iowa (xrmap collection).svg |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1992 United States Senate election in Iowa |
| Previous Year: | 1992 |
| Next Election: | 2004 United States Senate election in Iowa |
| Next Year: | 2004 |
| Election Date: | November 3, 1998 |
| Image1: | Chuck Grassley official photo.jpg |
| Nominee1: | Chuck Grassley |
| Party1: | Republican Party (United States) |
| Popular Vote1: | 648,480 |
| Percentage1: | 68.41% |
| Nominee2: | David Osterberg |
| Party2: | Democratic Party (United States) |
| Popular Vote2: | 289,049 |
| Percentage2: | 30.49% |
| Map Size: | 240px |
| U.S. Senator | |
| Before Election: | Chuck Grassley |
| Before Party: | Republican Party (United States) |
| After Election: | Chuck Grassley |
| After Party: | Republican Party (United States) |
The 1998 United States Senate election in Iowa was held November 3, 1998. Incumbent Republican United States Senator Chuck Grassley sought re-election to a fourth term in the United States Senate, running against former State Representative David Osterberg, who won the Democratic nomination unopposed. Grassley had not faced a competitive election since 1980; this year proved no different, and Grassley defeated Osterberg in a landslide.