Knebworth House is an English country house in the parish of Knebworth in Hertfordshire, England. It is a Grade II* listed building. Its gardens are also listed Grade II* on the Register of Historic Parks and Gardens. In its surrounding park are the medieval St. Mary's Church and the Lytton family mausoleum. It was the seat of the Earl of Lytton, and now the house of the family of the Baron Cobbold of Knebworth.