Merrimack
- Country: United States
- State: New Hampshire
- Population: 25,580 (2016)
- Latitude: 42° 51.9' N (42.865°)
- Longitude: 71° 29.6' W (-71.494°)
- Elevation: 57 m/186 ft. above sea level
- Time zone: America/New_York (UTC -05:00); DST observed (UTC -04:00)