Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Waterbury | 1 | 115,360 | 113,880 | 0.32% | 4,040 | 28.6 | City |
| Bristol | 2 | 61,892 | 60,727 | 0.47% | 2,344 | 26.4 | City |
| Shelton | 3 | 42,604 | 40,762 | 1.09% | 1,391 | 30.6 | City |
| Naugatuck | 4 | 31,929 | 31,492 | 0.34% | 1,949 | 16.4 | Borough |
| Cheshire | 5 | 29,403 | 28,612 | 0.69% | 895 | 32.8 | Township |
| Watertown | 6 | 22,365 | 22,085 | 0.41% | 771 | 29.0 | Township |
| Southbury | 7 | 20,260 | 19,861 | 0.66% | 519 | 39.0 | Township |
| Ansonia | 8 | 19,048 | 18,886 | 0.21% | 3,165 | 6.0 | City |
| Seymour | 9 | 17,108 | 16,714 | 0.91% | 1,178 | 14.5 | Township |
| Wolcott | 10 | 16,426 | 16,101 | 0.72% | 806 | 20.4 | Township |
| Oxford | 11 | 13,304 | 12,708 | 1.36% | 406 | 32.7 | Township |
| Derby | 12 | 12,437 | 12,312 | 0.25% | 2,460 | 5.1 | City |
| Plymouth | 13 | 11,818 | 11,648 | 0.44% | 540 | 21.9 | Township |
| Woodbury | 14 | 9,922 | 9,712 | 0.61% | 273 | 36.4 | Township |
| Prospect | 15 | 9,521 | 9,372 | 0.44% | 670 | 14.2 | Township |
| Middlebury | 16 | 8,054 | 7,583 | 1.49% | 454 | 17.8 | Township |
| Thomaston | 17 | 7,533 | 7,436 | 0.43% | 628 | 12.0 | Township |
| Beacon Falls | 18 | 6,284 | 6,007 | 1.26% | 650 | 9.7 | Township |
| Bethlehem | 19 | 3,433 | 3,387 | 0.35% | 177 | 19.4 | Township |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Waterbury is the largest city in Naugatuck Valley Planning Region.
Bethlehem is the smallest city in Naugatuck Valley Planning Region.
There are 19 cities in Naugatuck Valley Planning Region, Connecticut.