18 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Genoa | 1 | 29,069 | 24,945 | 1.96% | 1,641 | 18 | Township |
| Port Clinton | 2 | 5,864 | 6,016 | -0.42% | 2,752 | 2 | City |
| Danbury | 3 | 4,840 | 4,919 | -0.25% | 268 | 18 | Township |
| Clay | 4 | 4,693 | 4,809 | -0.34% | 180 | 26 | Township |
| Allen | 5 | 3,666 | 3,763 | -0.38% | 145 | 25 | Township |
| Catawba Island | 6 | 3,637 | 3,705 | -0.27% | 649 | 6 | Township |
| Harris | 7 | 2,853 | 2,936 | -0.42% | 101 | 28 | Township |
| Oak Harbor | 8 | 2,775 | 2,819 | -0.25% | 1,749 | 2 | Village |
| Benton | 9 | 2,353 | 2,417 | -0.42% | 53 | 44 | Township |
| Genoa | 10 | 2,167 | 2,224 | -0.41% | 1,085 | 2 | Village |
| Elmore | 11 | 1,357 | 1,399 | -0.51% | 1,467 | 1 | Village |
| Erie | 12 | 1,156 | 1,163 | -0.17% | 94 | 12 | Township |
| Bay | 13 | 1,108 | 1,127 | -0.27% | 69 | 16 | Township |
| Marblehead | 14 | 828 | 849 | -0.36% | 261 | 3 | Village |
| Put-in-Bay | 15 | 789 | 807 | -0.25% | 159 | 5 | Township |
| Rocky Ridge | 16 | 304 | 310 | -0.33% | 303 | 1 | Village |
| Clay Center | 17 | 242 | 259 | -1.22% | 239 | 1 | Village |
| Put-in-Bay | 18 | 150 | 155 | -0.66% | 342 | 0 | Village |
Genoa is the largest city in Ottawa County, with a population of 29,069.
Put-in-Bay is the smallest city in Ottawa County, with a population of 150.
There are 18 cities in Ottawa County, Ohio.