18 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Manhattan | 1 | 54,837 | 54,151 | 0.25% | 2,732 | 20 | City |
| Manhattan | 2 | 2,290 | 2,216 | 1.55% | 72 | 32 | Township |
| Ogden | 3 | 2,088 | 2,073 | 1.16% | 169 | 12 | Township |
| Ogden | 4 | 1,653 | 1,668 | -0.18% | 988 | 2 | City |
| Riley | 5 | 958 | 943 | 0.31% | 1,886 | 1 | City |
| Grant | 6 | 911 | 893 | 1.45% | 26 | 36 | Township |
| Wildcat | 7 | 865 | 843 | 1.53% | 30 | 29 | Township |
| Bala | 8 | 703 | 677 | 1.88% | 17 | 42 | Township |
| Sherman | 9 | 592 | 578 | 1.54% | 20 | 29 | Township |
| Leonardville | 10 | 443 | 431 | 0.45% | 1,448 | 0 | City |
| Keats | 11 | 350 | 210 | 7.03% | 759 | 0 | CDP |
| Zeandale | 12 | 344 | 335 | 1.78% | 6 | 60 | Township |
| Jackson | 13 | 298 | 295 | 1.02% | 9 | 32 | Township |
| Swede Creek | 14 | 172 | 169 | 1.18% | 4 | 49 | Township |
| Randolph | 15 | 157 | 159 | -0.63% | 571 | 0 | City |
| Fancy Creek | 16 | 91 | 90 | 1.11% | 3 | 32 | Township |
| Center | 17 | 77 | 76 | 1.32% | 2 | 32 | Township |
| May Day | 18 | 73 | 70 | 1.39% | 2 | 31 | Township |
Manhattan is the largest city in Riley County, with a population of 54,837.
May Day is the smallest city in Riley County, with a population of 73.
There are 18 cities in Riley County, Kansas.