20 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Gallipolis | 1 | 4,672 | 4,751 | -0.19% | 465 | 10 | Township |
| Gallipolis | 2 | 3,272 | 3,319 | -0.3% | 910 | 4 | Village |
| Addison | 3 | 2,084 | 2,114 | -0.24% | 78 | 27 | Township |
| Raccoon | 4 | 2,032 | 2,044 | -0.1% | 55 | 37 | Township |
| Clay | 5 | 1,720 | 1,750 | -0.35% | 79 | 22 | Township |
| Huntington | 6 | 1,444 | 1,444 | -0.07% | 40 | 37 | Township |
| Morgan | 7 | 1,332 | 1,356 | -0.37% | 43 | 31 | Township |
| Bidwell | 8 | 1,295 | 872 | 7.11% | 851 | 2 | CDP |
| Guyan | 9 | 1,115 | 1,125 | -0.18% | 35 | 32 | Township |
| Walnut | 10 | 975 | 991 | -0.31% | 24 | 41 | Township |
| Ohio | 11 | 910 | 928 | -0.33% | 39 | 23 | Township |
| Cheshire | 12 | 894 | 912 | -0.33% | 29 | 30 | Township |
| Rio Grande | 13 | 725 | 720 | 0.14% | 527 | 1 | Village |
| Miller | 14 | 669 | 539 | 7.21% | 675 | 1 | CDP |
| Vinton | 15 | 507 | 509 | 0.6% | 14 | 37 | Township |
| Crown City | 16 | 415 | 422 | -0.48% | 357 | 1 | Village |
| Kanauga | 17 | 302 | 98 | 2.72% | 1,045 | 0 | CDP |
| Vinton | 18 | 223 | 223 | 0% | 189 | 1 | Village |
| Cheshire | 19 | 120 | 123 | -0.83% | 156 | 1 | Village |
| Centerville (Thurman) | 20 | 86 | 88 | -1.15% | 860 | 0 | Village |
Gallipolis is the largest city in Gallia County, with a population of 4,672.
Centerville (Thurman) is the smallest city in Gallia County, with a population of 86.
There are 20 cities in Gallia County, Ohio.