5 cities
| City | County | 2026 Pop. ↓ |
|---|---|---|
| Danbury | Western CT Planning Region | 89,990 |
| Darien | Western CT Planning Region | 23,204 |
| Derby | Naugatuck Valley Planning Region | 13,216 |
| Durham | Lower CT River Valley Planning Region | 7,244 |
| Deep River | Lower CT River Valley Planning Region | 4,513 |