19 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Itasca | DuPage County | 9,228 |
| Island Lake | Lake County | 7,964 |
| Inverness | Cook County | 7,115 |
| Indian Head Park | Cook County | 3,796 |
| Ingalls Park | Will County | 3,049 |
| Ina | Jefferson County | 1,655 |
| Illiopolis | Sangamon County | 822 |
| Irvington | Washington County | 562 |
| Indian Creek | Lake County | 523 |
| Iuka | Marion County | 484 |
| Ipava | Fulton County | 417 |
| Industry | McDonough County | 386 |
| Irving | Montgomery County | 359 |
| Ivesdale | Champaign County | 248 |
| Indianola | Vermilion County | 216 |
| Iroquois | Iroquois County | 127 |
| Iola | Clay County | 95 |
| Irwin | Kankakee County | 66 |
| Illinois City | Rock Island County | 46 |