8 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Fairmont | 1 | 17,974 | 18,426 | -0.5% | 2,090 | 8.60 | City |
| Mannington | 2 | 1,893 | 1,950 | -0.58% | 1,732 | 1.09 | City |
| Barrackville | 3 | 1,195 | 1,210 | -0.25% | 1,734 | 0.69 | Town |
| Rivesville | 4 | 803 | 827 | -0.62% | 1,532 | 0.52 | Town |
| Grant Town | 5 | 665 | 687 | -0.6% | 1,262 | 0.53 | Town |
| Farmington | 6 | 404 | 388 | 0.75% | 973 | 0.41 | Town |
| Fairview | 7 | 368 | 373 | -0.27% | 1,314 | 0.28 | Town |
| Worthington | 8 | 173 | 178 | -0.57% | 297 | 0.58 | Town |
Fairmont is the largest city in Marion County, with a population of 17,974.
Worthington is the smallest city in Marion County.
There are 8 cities in Marion County, West Virginia.