| Fynn | |
| Pushpin Map: | United Kingdom Suffolk |
| Pushpin Map Caption: | Location of the river mouth within Suffolk |
| Subdivision Type1: | Country |
| Subdivision Name1: | England |
| Subdivision Type3: | Region |
| Subdivision Name3: | Suffolk |
| Length: | 13.622km (08.464miles)[1] |
| Source1 Location: | Witnesham |
| Source1 Coordinates: | 52.2799°N 1.3048°W |
| Source1 Elevation: | 60m (200feet) |
| Mouth Location: | Martlesham |
| Mouth Coordinates: | 52.0767°N 1.2953°W |
| Mouth Elevation: | 0m (00feet) |
| River System: | River Deben |
| Custom Label: | Water Body ID |
| Custom Data: | GB105035040330 |
The River Fynn is a waterway in Suffolk which joins the River Deben. Its source is at Witnesham and it joins the Deben at Woodbridge.[2]