19 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Itasca | DuPage County | 9,497 |
| Island Lake | Lake County | 8,073 |
| Inverness | Cook County | 7,386 |
| Indian Head Park | Cook County | 3,930 |
| Ingalls Park | Will County | 3,049 |
| Ina | Jefferson County | 1,647 |
| Illiopolis | Sangamon County | 831 |
| Irvington | Washington County | 562 |
| Indian Creek | Lake County | 535 |
| Iuka | Marion County | 485 |
| Ipava | Fulton County | 422 |
| Industry | McDonough County | 385 |
| Irving | Montgomery County | 360 |
| Ivesdale | Champaign County | 261 |
| Indianola | Vermilion County | 217 |
| Iroquois | Iroquois County | 130 |
| Iola | Clay County | 95 |
| Irwin | Kankakee County | 66 |
| Illinois City | Rock Island County | 46 |