21 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Lima | 1 | 34,304 | 35,529 | -0.71% | 2,519 | 13.62 | City |
| American township | 2 | 14,344 | 14,509 | -0.09% | 597 | 24.02 | Township |
| Fort Shawnee | 3 | 7,974 | 5,835 | 7.15% | 838 | 9.51 | CDP |
| Delphos | 4 | 7,028 | 7,110 | -0.23% | 2,116 | 3.32 | City |
| Lafayette township | 5 | 6,233 | 6,073 | 0.65% | 272 | 22.91 | Township |
| Richland township | 6 | 5,779 | 5,882 | -0.19% | 139 | 41.65 | Township |
| Lafayette township | 7 | 4,375 | 4,277 | 0.69% | 177 | 24.69 | Township |
| Bluffton | 8 | 3,863 | 3,962 | -0.52% | 1,045 | 3.69 | Village |
| Auglaize township | 9 | 2,827 | 2,759 | 0.43% | 79 | 35.99 | Township |
| Spencerville | 10 | 2,138 | 2,202 | -0.6% | 2,216 | 0.96 | Village |
| Elida | 11 | 1,883 | 1,925 | -0.42% | 1,616 | 1.17 | Village |
| Cridersville | 12 | 1,711 | 1,798 | -0.98% | 1,426 | 1.20 | Village |
| Sugar Creek township | 13 | 1,189 | 1,222 | -0.34% | 49 | 24.09 | Township |
| Westminster | 14 | 770 | 565 | 7.09% | 423 | 1.82 | CDP |
| Cairo | 15 | 495 | 512 | -0.6% | 1,787 | 0.28 | Village |
| McGuffey | 16 | 453 | 465 | -0.44% | 1,218 | 0.37 | Village |
| Harrod | 17 | 423 | 427 | -0.24% | 1,808 | 0.23 | Village |
| Lafayette | 18 | 393 | 400 | -0.25% | 1,687 | 0.23 | Village |
| Beaverdam | 19 | 309 | 321 | -0.64% | 490 | 0.63 | Village |
| Gomer | 20 | 240 | 167 | 7.14% | 105 | 2.29 | CDP |
| Lafayette | 21 | 116 | 188 | -4.92% | 111 | 1.05 | CDP |
Lima is the largest city in Allen County, with a population of 34,304.
Lafayette is the smallest city in Allen County.
There are 21 cities in Allen County, Ohio.