| Fort Sage Mountains | |
| Country: | United States |
| Subdivision1 Type: | States |
| Subdivision2 Type: | Region |
| Subdivision3 Type: | Districts |
| Topo Map: | State Line Peak |
| Topo Maker: | USGS |
| Range Coordinates: | 40.0299°N -119.9813°W |
| Elevation M: | 2393 |
| Map: | California |
| Map Relief: | yes |
| Map Size: | 220 |
The Fort Sage Mountains are a mountain range running across the state borders in western Washoe County, Nevada and eastern Lassen County, California.