The largest county in Ohio
There are two right answers. By land area it is Ashtabula County; by population it is Franklin County. Which one you want depends on what you meant by largest.
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025. Retrieved 30 August 2026.
By land area
| Rank | Name | Land area | Population |
|---|---|---|---|
| 1 | Ashtabula County | 702.4 sq mi | 96,713 |
| 2 | Ross County | 689.2 sq mi | 76,429 |
| 3 | Licking County | 682.4 sq mi | 185,564 |
| 4 | Muskingum County | 664.5 sq mi | 87,014 |
| 5 | Washington County | 632.2 sq mi | 58,389 |
| 6 | Trumbull County | 617.6 sq mi | 198,972 |
| 7 | Wood County | 617.2 sq mi | 134,176 |
| 8 | Scioto County | 610.2 sq mi | 71,365 |
| 9 | Darke County | 598.1 sq mi | 51,520 |
| 10 | Adams County | 583.9 sq mi | 27,865 |
By population
| Rank | Name | Population | Density |
|---|---|---|---|
| 1 | Franklin County | 1,361,536 | 2,557 per sq mi |
| 2 | Cuyahoga County | 1,232,925 | 2,696 per sq mi |
| 3 | Hamilton County | 838,418 | 2,068 per sq mi |
| 4 | Montgomery County | 539,598 | 1,170 per sq mi |
| 5 | Summit County | 538,376 | 1,305 per sq mi |
| 6 | Lucas County | 423,347 | 1,246 per sq mi |
| 7 | Butler County | 400,128 | 858 per sq mi |
| 8 | Stark County | 373,771 | 650 per sq mi |
| 9 | Lorain County | 323,219 | 659 per sq mi |
| 10 | Warren County | 257,181 | 641 per sq mi |
And the smallest
More on Ohio
Rebuilt from source data 30 August 2026. How these figures are produced.