Roughdown Common is a 3.6-hectare (8.9-acre) biological Site of Special Scientific Interest in Hemel Hempstead in Hertfordshire. The planning authority is Dacorum Borough Council. The site is Common land, and it is owned by the Box Moor Trust having been officially bought by the trust in April 1886 from the Dean and Chapter of St Paul's. It is part of the Chilterns Area of Outstanding Natural Beauty. The Common is a steeply sloping chalk hill in south Hemel Hempstead.