15 cities
| City | 2025 Pop. ↓ |
|---|---|
| Islington | 319,143 |
| Ipswich | 178,835 |
| Inverness | 47,060 |
| Ilkeston | 38,587 |
| Irvine | 33,740 |
| Isleworth | 20,500 |
| Irlam | 19,442 |
| Isle of Lewis | 18,500 |
| Ilkley | 14,809 |
| Ingleby Greenhow | 14,608 |
| Inverurie | 12,760 |
| Ivybridge | 11,851 |
| Ince-in-Makerfield | 11,185 |
| Ilfracombe | 11,184 |
| Immingham | 10,750 |