Decatur
- Country: United States
- State: Indiana
- Population: 9,524 (2016)
- Latitude: 40° 49.8' N (40.8306°)
- Longitude: 84° 55.7' W (-84.92913°)
- Elevation: 244 m/801 ft. above sea level
- Time zone: America/Indiana/Indianapolis (UTC -05:00); DST observed (UTC -04:00)