10 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Jacksonville | 1 | 70,232 | 73,270 | -0.86% | 1,439 | 49 | City |
| Piney Green | 2 | 15,136 | 14,309 | 0.82% | 1,110 | 14 | CDP |
| Half Moon | 3 | 8,388 | 8,384 | 0.02% | 1,130 | 7 | CDP |
| Holly Ridge | 4 | 6,146 | 4,243 | 6.59% | 1,454 | 4 | Town |
| Swansboro | 5 | 4,266 | 3,760 | 2.42% | 1,909 | 2 | Town |
| Richlands | 6 | 2,483 | 2,296 | 1.51% | 1,504 | 2 | Town |
| Pumpkin Center | 7 | 2,133 | 1,850 | -0.28% | 1,684 | 1 | CDP |
| Sneads Ferry | 8 | 2,014 | 2,326 | -2.04% | 530 | 4 | CDP |
| North Topsail Beach | 9 | 1,099 | 1,007 | 1.67% | 177 | 6 | Town |
| Topsail Beach | 10 | 508 | 467 | 1.6% | 116 | 4 | Town |
Jacksonville is the largest city in Onslow County, with a population of 70,232.
Topsail Beach is the smallest city in Onslow County, with a population of 508.
There are 10 cities in Onslow County, North Carolina.