10 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Jacksonville | 1 | 71,517 | 74,922 | -0.94% | 1,465 | 48.80 | City |
| Piney Green | 2 | 15,136 | 14,309 | 0.82% | 1,110 | 13.63 | CDP |
| Half Moon | 3 | 8,388 | 8,384 | 0.02% | 1,130 | 7.42 | CDP |
| Holly Ridge | 4 | 5,787 | 4,244 | 5.64% | 1,369 | 4.23 | Town |
| Swansboro | 5 | 4,391 | 3,756 | 2.98% | 1,965 | 2.23 | Town |
| Richlands | 6 | 2,495 | 2,294 | 1.63% | 1,511 | 1.65 | Town |
| Pumpkin Center | 7 | 2,133 | 1,850 | -0.28% | 1,684 | 1.27 | CDP |
| Sneads Ferry | 8 | 2,014 | 2,326 | -2.04% | 530 | 3.80 | CDP |
| North Topsail Beach | 9 | 1,109 | 1,009 | 1.84% | 178 | 6.22 | Town |
| Topsail Beach | 10 | 517 | 466 | 1.97% | 118 | 4.39 | Town |
Jacksonville is the largest city in Onslow County, with a population of 71,517.
Topsail Beach is the smallest city in Onslow County.
There are 10 cities in Onslow County, North Carolina.