Monks Wood is a 157-hectare (390-acre) National Nature Reserve north-west of Huntingdon in Cambridgeshire, and a Nature Conservation Review site, Grade I. A slightly more extensive area of 169.3 hectares (418 acres) is the Monks Wood and The Odd Quarter biological Site of Special Scientific Interest.
The site is described by Natural England as one of Britain's most essential lowland woods. It is mainly of the wet ash-maple type, with a creamy shrub layer that was formerly coppiced. Trees include the rare wild service tree, particularly in The Odd Quarter. There is ground flora typical of ancient woodland, together with woodland rides, ponds, streams, and herb-rich grassland.