Old Sulehay Forest is a 34.8-hectare (86-acre) biological Site of Special Scientific Interest east of King's Cliffe in Northamptonshire.

[1][2] It is part of the 85-hectare (210-acre) Old Sulehay nature reserve, which is managed by the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire.

[3] This ancient forest has a number of different soil conditions and coppice types, and the ground flora is diverse.

Abundant herbs include dog's mercury, bracken, bramble, ramsons, wood anemone and bluebells.

[4] There is access by footpaths from Wansford Road.