Hardin
- Country: United States
- State: Montana
- Population: 3,829 (2016)
- Latitude: 45° 43.9' N (45.73248°)
- Longitude: 107° 36.7' W (-107.61203°)
- Elevation: 886 m/2,907 ft. above sea level
- Time zone: America/Denver (UTC -07:00); DST observed (UTC -06:00)