Bedford Purlieus is 211 hectares (520 acres) of ancient woodland in Cambridgeshire, in the United Kingdom. It is a national nature reserve and Site of Special Scientific Interest owned and managed by the Forestry Commission. Situated in Thornhaugh civil parish, 10 km south of Stamford and 14 km (8.7 mi) west of Peterborough, the wood is within the Peterborough unitary authority area of Cambridgeshire, and borders Northamptonshire. In Roman times it was an iron smelting centre, during the medieval period it was in the Royal Forest of Rockingham, and later became part of the estates of the Duke of Bedford. Bedford Purlieus appears to have been continuously wooded at least from Roman times, and probably since the ice receded. The woodland may have the richest range of vascular plants of any English lowland wood.