6 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Jacksonville | 1 | 70,232 | 73,270 | -0.86% | 1,407 | 50 | City |
| Holly Ridge | 2 | 6,146 | 4,243 | 6.59% | 1,397 | 4 | Town |
| Swansboro | 3 | 4,266 | 3,760 | 2.42% | 1,909 | 2 | Town |
| Richlands | 4 | 2,483 | 2,296 | 1.51% | 1,225 | 2 | Town |
| North Topsail Beach | 5 | 1,099 | 1,007 | 1.67% | 177 | 6 | Town |
| Topsail Beach | 6 | 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 6 cities in Onslow County, North Carolina.