21 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 |
| Fort Shawnee | 3 | 7,974 | 5,835 | 7.15% | 838 | 10 | CDP |
| Delphos | 4 | 7,063 | 7,115 | -0.16% | 2,126 | 3 | City |
| Lafayette | 5 | 6,225 | 6,074 | 0.55% | 272 | 23 | Township |
| Richland | 6 | 5,752 | 5,883 | -0.4% | 138 | 42 | Township |
| Lafayette | 7 | 4,348 | 4,281 | 0.37% | 176 | 25 | Township |
| Bluffton | 8 | 3,860 | 3,964 | -0.54% | 1,045 | 4 | Village |
| Auglaize | 9 | 2,831 | 2,763 | 0.43% | 79 | 36 | Township |
| Spencerville | 10 | 2,154 | 2,202 | -0.46% | 2,232 | 1 | Village |
| Elida | 11 | 1,898 | 1,926 | -0.32% | 1,629 | 1 | Village |
| Cridersville | 12 | 1,732 | 1,796 | -0.74% | 1,443 | 1 | Village |
| Sugar Creek | 13 | 1,196 | 1,224 | -0.08% | 50 | 24 | Township |
| Westminster | 14 | 770 | 565 | 7.09% | 423 | 2 | CDP |
| Cairo | 15 | 505 | 518 | -0.59% | 1,823 | 0 | Village |
| McGuffey | 16 | 455 | 463 | -0.44% | 1,223 | 0 | Village |
| Harrod | 17 | 426 | 429 | -0.23% | 1,821 | 0 | Village |
| Lafayette | 18 | 393 | 401 | -0.51% | 1,687 | 0 | Village |
| Beaverdam | 19 | 312 | 321 | -0.64% | 495 | 1 | Village |
| Gomer | 20 | 240 | 167 | 7.14% | 105 | 2 | CDP |
| Lafayette | 21 | 116 | 188 | -4.92% | 111 | 1 | CDP |
Lima is the largest city in Allen County, with a population of 34,491.
Lafayette is the smallest city in Allen County, with a population of 116.
There are 21 cities in Allen County, Ohio.