Firth
- County:
- Bingham County
- County Seat:
- No
- Area (mi²):
- 0.573
- State:
- Idaho
Firth is a city located in Bingham County, Idaho. Firth has a 2026 population of 542. Firth is currently growing at a rate of 0.18% annually and its population has increased by 4.03% since the most recent census, which recorded a population of 521 in 2020.