17 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Lima | 1 | 34,491 | 35,483 | -0.57% | 2,533 | 14 | City |
| American | 2 | 14,468 | 14,563 | 0.16% | 602 | 24 | Township |
| Delphos | 3 | 7,063 | 7,115 | -0.16% | 2,126 | 3 | City |
| Lafayette | 4 | 6,225 | 6,074 | 0.55% | 272 | 23 | Township |
| Richland | 5 | 5,752 | 5,883 | -0.4% | 138 | 42 | Township |
| Lafayette | 6 | 4,348 | 4,281 | 0.37% | 176 | 25 | Township |
| Bluffton | 7 | 3,860 | 3,964 | -0.54% | 1,045 | 4 | Village |
| Auglaize | 8 | 2,831 | 2,763 | 0.43% | 79 | 36 | Township |
| Spencerville | 9 | 2,154 | 2,202 | -0.46% | 2,232 | 1 | Village |
| Elida | 10 | 1,898 | 1,926 | -0.32% | 1,629 | 1 | Village |
| Cridersville | 11 | 1,732 | 1,796 | -0.74% | 1,443 | 1 | Village |
| Sugar Creek | 12 | 1,196 | 1,224 | -0.08% | 50 | 24 | Township |
| Cairo | 13 | 505 | 518 | -0.59% | 1,823 | 0 | Village |
| McGuffey | 14 | 455 | 463 | -0.44% | 1,223 | 0 | Village |
| Harrod | 15 | 426 | 429 | -0.23% | 1,821 | 0 | Village |
| Lafayette | 16 | 393 | 401 | -0.51% | 1,687 | 0 | Village |
| Beaverdam | 17 | 312 | 321 | -0.64% | 495 | 1 | Village |
Lima is the largest city in Allen County, with a population of 34,491.
Beaverdam is the smallest city in Allen County, with a population of 312.
There are 17 cities in Allen County, Ohio.