Susanville
- County:
- Lassen County
- County Seat:
- Yes
- Area (mi²):
- 7.918
- State:
- California
Susanville is a city located in Lassen County, California. Susanville has a 2026 population of 12,359. It is also the county seat of Lassen County. Susanville is currently declining at a rate of -2.28% annually and its population has decreased by -24.62% since the most recent census, which recorded a population of 16,396 in 2020.