21 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Star | Ada County | 19,590 |
| Sandpoint | Bonner County | 10,886 |
| Shelley | Bingham County | 5,416 |
| St. Anthony | Fremont County | 4,236 |
| Salmon | Lemhi County | 3,413 |
| Soda Springs | Caribou County | 3,204 |
| Spirit Lake | Kootenai County | 2,566 |
| St. Maries | Benewah County | 2,545 |
| Sugar City | Madison County | 2,372 |
| Shoshone | Lincoln County | 1,770 |
| Sun Valley | Blaine County | 1,757 |
| Smelterville | Shoshone County | 734 |
| Silverton | Shoshone County | 720 |
| Swan Valley | Bonneville County | 343 |
| St. Charles | Bear Lake County | 201 |
| Stites | Idaho County | 199 |
| Sweetwater | Nez Perce County | 179 |
| Stanley | Custer County | 120 |
| Smiths Ferry | Idaho County | 102 |
| State Line | Kootenai County | 37 |
| Spencer | Clark County | 29 |