| City | County | 2026 Pop. ↓ |
|---|---|---|
| Itasca | DuPage County | 9,471 |
| Island Lake | Lake County | 8,048 |
| Inverness | Cook County | 7,375 |
| Indian Head Park | Cook County | 3,936 |
| Ingalls Park | Will County | 2,891 |
| Ina | Jefferson County | 1,602 |
| Illiopolis | Sangamon County | 829 |
| Irvington | Washington County | 562 |
| Indian Creek | Lake County | 530 |
| Iuka | Marion County | 487 |
| Ipava | Fulton County | 413 |
| Industry | McDonough County | 380 |
| Irving | Montgomery County | 362 |
| Ivesdale | Champaign County | 253 |
| Indianola | Vermilion County | 217 |
| Iroquois | Iroquois County | 130 |
| Iola | Clay County | 95 |
| Irwin | Kankakee County | 62 |
| Illinois City | Rock Island County | 22 |