The Water of Cruden is a short broadly east-flowing river in Buchan in northeast Scotland.

The harbour of Port Erroll stands at the point that the tidal channel enters the sea.

The course of the lowest section of the river was diverted in the 19th century; it is shown in John Thomson's Atlas of Scotland, 1832, as reaching the sea at what is now termed Old Water Moo', a gorge inlet on a peninsula north of the Bay of Cruden.

[3] An 1872 Ordnance Survey map shows the river flowing into the Bay of Cruden.

[4] The OS name book for Aberdeenshire notes the diversion in its entry for Old Water Moo', a sea inlet into which the river once discharged.