24 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Genoa township | 1 | 28,709 | 24,946 | 2.58% | 1,620 | 17.72 | Township |
| Port Clinton | 2 | 5,877 | 6,017 | -0.47% | 2,758 | 2.13 | City |
| Danbury township | 3 | 4,838 | 4,914 | -0.31% | 268 | 18.08 | Township |
| Clay township | 4 | 4,691 | 4,810 | -0.53% | 180 | 26.04 | Township |
| Ballville | 5 | 3,800 | 3,537 | 1.47% | 840 | 4.52 | CDP |
| Allen township | 6 | 3,669 | 3,764 | -0.52% | 145 | 25.27 | Township |
| Catawba Island township | 7 | 3,641 | 3,706 | -0.38% | 650 | 5.60 | Township |
| Harris township | 8 | 2,855 | 2,932 | -0.52% | 101 | 28.25 | Township |
| Oak Harbor | 9 | 2,785 | 2,820 | -0.25% | 1,755 | 1.59 | Village |
| Benton township | 10 | 2,355 | 2,417 | -0.55% | 53 | 44.29 | Township |
| Genoa | 11 | 2,172 | 2,224 | -0.46% | 1,361 | 1.60 | Village |
| Stony Prairie | 12 | 1,835 | 1,632 | 2.06% | 1,144 | 1.60 | CDP |
| Curtice | 13 | 1,495 | 1,251 | -0.13% | 406 | 3.68 | CDP |
| Elmore | 14 | 1,359 | 1,396 | -0.51% | 1,469 | 0.93 | Village |
| Erie township | 15 | 1,154 | 1,161 | -0.17% | 94 | 12.24 | Township |
| Bay township | 16 | 1,106 | 1,126 | -0.36% | 69 | 16.13 | Township |
| Marblehead | 17 | 831 | 851 | -0.48% | 262 | 3.17 | Village |
| Put-in-Bay township | 18 | 796 | 813 | -0.38% | 161 | 4.95 | Township |
| Lakeside | 19 | 561 | 686 | -1.58% | 815 | 0.69 | CDP |
| Williston | 20 | 323 | 419 | -3.29% | 529 | 0.61 | CDP |
| Rocky Ridge | 21 | 306 | 310 | -0.33% | 305 | 1 | Village |
| Clay Center | 22 | 245 | 260 | -1.21% | 242 | 1.01 | Village |
| Put-in-Bay | 23 | 149 | 153 | -0.67% | 339 | 0.44 | Village |
| Wightmans Grove | 24 | 20 | 40 | 5.26% | 142 | 0.14 | CDP |
Genoa township is the largest city in Ottawa County, with a population of 28,709.
Wightmans Grove is the smallest city in Ottawa County.
There are 24 cities in Ottawa County, Ohio.