6 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Ellensburg | 1 | 20,680 | 21,627 | -0.76% | 2,341 | 9 | City |
| Union Gap | 2 | 6,596 | 6,553 | 0.11% | 1,183 | 6 | City |
| Cle Elum | 3 | 2,325 | 2,177 | 1.09% | 518 | 4 | City |
| Kittitas | 4 | 1,441 | 1,453 | -0.14% | 1,845 | 1 | City |
| Roslyn | 5 | 959 | 961 | 0% | 218 | 4 | City |
| South Cle Elum | 6 | 577 | 561 | 0.52% | 1,435 | 0 | Town |
Ellensburg is the largest city in Kittitas County, with a population of 20,680.
South Cle Elum is the smallest city in Kittitas County, with a population of 577.
There are 6 cities in Kittitas County, Washington.