| River Ainse (Eyn) | |
| Pushpin Map: | United Kingdom Norfolk |
| Pushpin Map Caption: | Location of the river mouth within Norfolk |
| Subdivision Type1: | Country |
| Subdivision Name1: | England |
| Subdivision Type2: | State |
| Subdivision Name2: | Norfolk |
| Subdivision Type3: | Region |
| Subdivision Name3: | East of England |
| Subdivision Type4: | District |
| Subdivision Name4: | Broadland |
| Length: | 14.2km (08.8miles) |
| Source1 Location: | near Heydon |
| Source1 Coordinates: | 52.788°N 1.0917°W |
| Source1 Elevation: | 47m (154feet) |
| Mouth: | River Wensum |
| Mouth Location: | Lenwade |
| Mouth Coordinates: | 52.725°N 1.1204°W |
| Mouth Elevation: | 14m (46feet) |
The River Ainse (or Eyn) is a small river in the county of Norfolk. It is a tributary of the River Wensum which it merges with at Lenwade.[1] The River Ainse has several tributaries also.
The watermill located on the river at Great Witchingham is known as Eade's Mill.[2] The mill was built in 1666. Until 1948 the waterwheel was still in working order. By 1972 the watermill was still being used as a hammer mill to grind up pig meal and was powered by electricity. Today, the watermill and its surrounding buildings are listed.