11 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Billings | 1 | 123,290 | 117,224 | 0.99% | 2,705 | 45.57 | City |
| Laurel | 2 | 7,177 | 7,217 | -0.11% | 2,755 | 2.60 | City |
| Shepherd | 3 | 836 | 944 | 2.58% | 376 | 2.22 | CDP |
| Worden | 4 | 484 | 481 | -1.43% | 245 | 1.98 | CDP |
| Huntley | 5 | 364 | 522 | -1.36% | 239 | 1.52 | CDP |
| Ballantine | 6 | 260 | 352 | -1.52% | 286 | 0.91 | CDP |
| Nibbe | 7 | 161 | 120 | 7.33% | 694 | 0.23 | CDP |
| Custer | 8 | 143 | 151 | -0.69% | 454 | 0.32 | CDP |
| Broadview | 9 | 136 | 140 | -0.73% | 519 | 0.26 | Town |
| Acton | 10 | 99 | 76 | 7.61% | 413 | 0.24 | CDP |
| Pompeys Pillar | 11 | 29 | 86 | 7.41% | 149 | 0.20 | CDP |
Billings is the largest city in Yellowstone County, with a population of 123,290.
Pompeys Pillar is the smallest city in Yellowstone County, with a population of 29.
There are 11 cities in Yellowstone County, Montana.