| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Norwich | 1 | 40,000 | 40,035 | 0% | 1,425 | 28 | City |
| Groton | 2 | 39,146 | 38,339 | 0.02% | 1,258 | 31 | Township |
| New London | 3 | 28,310 | 26,793 | 1.1% | 5,049 | 6 | City |
| Windham | 4 | 24,131 | 23,867 | -0.03% | 899 | 27 | Township |
| Waterford | 5 | 20,929 | 19,577 | 2.42% | 637 | 33 | Township |
| East Lyme | 6 | 19,430 | 18,431 | 1.08% | 571 | 34 | Township |
| Stonington | 7 | 18,862 | 18,310 | 0.16% | 488 | 39 | Township |
| Montville | 8 | 18,058 | 18,044 | 0.32% | 432 | 42 | Township |
| Colchester | 9 | 15,838 | 15,520 | 0.08% | 324 | 49 | Township |
| Ledyard | 10 | 15,613 | 15,390 | 0.08% | 409 | 38 | Township |
| Griswold | 11 | 11,690 | 11,421 | 0% | 337 | 35 | Township |
| Lebanon | 12 | 7,144 | 7,123 | 0.03% | 132 | 54 | Township |
| North Stonington | 13 | 5,270 | 5,149 | 0.53% | 97 | 54 | Township |
| Preston | 14 | 4,882 | 4,791 | 0.18% | 158 | 31 | Township |
| Salem | 15 | 4,333 | 4,177 | 0.21% | 150 | 29 | Township |
| Lisbon | 16 | 4,268 | 4,187 | 0.19% | 262 | 16 | Township |
| Sprague | 17 | 2,958 | 2,964 | 0.14% | 223 | 13 | Township |
| Bozrah | 18 | 2,421 | 2,407 | 0.17% | 121 | 20 | Township |
| Franklin | 19 | 1,932 | 1,858 | 0.89% | 98 | 20 | Township |
Norwich is the largest city in Southeastern Connecticut Planning Region, with a population of 40,000.
Franklin is the smallest city in Southeastern Connecticut Planning Region, with a population of 1,932.
There are 19 cities in Southeastern Connecticut Planning Region, Connecticut.