| Afon Cadnant | |
|---|---|
 Clapper bridge over Afon Cadnant | |
  Location on Anglesey | |
| Location | |
| Country | Wales |
| Physical characteristics | |
| Mouth | Menai Strait |
The Afon Cadnant (English: River Cadnant) is a small river on Anglesey, North Wales in the United Kingdom, which drains to the Menai Strait about 1 km (0.62 mi) north-east of the Menai Suspension Bridge. The river drains a largely agricultural area from Llandegfan to Llansadwrn and beyond, with feeder tributaries extending up towards Pentraeth forest.
Within the catchment are some artificial fishing ponds and a number of beef and dairy farms.
More notable are the remains and ruins of a number of water mills, especially in the lower section before the river enters the strait. Up until the end of the 18th century it appears that great efforts were made to extract all the energy from the river to grind corn. This reflects the history of Anglesey as the bread-basket of Wales.