20 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Pleasant township | 1 | 7,911 | 8,082 | -0.38% | 204 | 38.81 | Township |
| Kenton | 2 | 7,764 | 7,954 | -0.49% | 1,553 | 5 | City |
| Liberty township | 3 | 7,091 | 7,076 | 0.55% | 198 | 35.84 | Township |
| Ada | 4 | 5,280 | 5,334 | -0.21% | 2,474 | 2.13 | Village |
| Buck township | 5 | 2,328 | 2,336 | 0% | 76 | 30.54 | Township |
| Hale township | 6 | 1,528 | 1,551 | -0.07% | 42 | 36.47 | Township |
| Dudley township | 7 | 1,434 | 1,475 | -0.35% | 38 | 37.35 | Township |
| Blanchard township | 8 | 1,387 | 1,413 | -0.36% | 58 | 24.01 | Township |
| Forest | 9 | 1,317 | 1,351 | -0.53% | 788 | 1.67 | Village |
| McDonald township | 10 | 863 | 881 | -0.35% | 20 | 42.88 | Township |
| Alger | 11 | 813 | 840 | -0.61% | 2,747 | 0.30 | Village |
| Dunkirk | 12 | 745 | 774 | -0.8% | 1,132 | 0.66 | Village |
| Washington township | 13 | 704 | 722 | -0.28% | 20 | 35.86 | Township |
| Roundhead township | 14 | 630 | 651 | -0.63% | 24 | 25.86 | Township |
| Taylor Creek township | 15 | 598 | 597 | 0.67% | 21 | 27.86 | Township |
| Mount Victory | 16 | 588 | 605 | -0.51% | 697 | 0.84 | Village |
| Lynn township | 17 | 568 | 591 | -0.87% | 23 | 25.05 | Township |
| Cessna township | 18 | 455 | 473 | -0.87% | 20 | 22.86 | Township |
| Ridgeway | 19 | 311 | 318 | -0.32% | 549 | 0.57 | Village |
| Dola | 20 | 135 | 141 | 0% | 162 | 0.83 | CDP |
Pleasant township is the largest city in Hardin County, with a population of 7,911.
Dola is the smallest city in Hardin County.
There are 20 cities in Hardin County, Ohio.