| City | County | 2026 Pop. ↓ |
|---|---|---|
| Janesville | Rock County | 67,140 |
| Jackson | Washington County | 8,397 |
| Jefferson | Jefferson County | 7,816 |
| Johnson Creek | Jefferson County | 3,451 |
| Juneau | Dodge County | 2,719 |
| Junction City | Portage County | 448 |
| Juda | Green County | 388 |
| Jim Falls | Chippewa County | 249 |
| Jolmaville | Ashland County | 124 |
| Jump River | Taylor County | 70 |