Seneca
- Country: United States
- State: Kansas
- Population: 2,048 (2016)
- Latitude: 39° 50.1' N (39.83417°)
- Longitude: 96° 3.9' W (-96.06417°)
- Elevation: 347 m/1,140 ft. above sea level
- Time zone: America/Chicago (UTC -06:00); DST observed (UTC -05:00)
- Alternate names: Castle Rock