Downhill Castle, also known as Downhill House, was a mansion built in the 18th century for Frederick Augustus Hervey,
4th Earl of Bristol at Downhill, Northern Ireland. Much of the building was destroyed by fire in 1851 before being rebuilt in the 1870s. It fell into disrepair after the Second World War. Downhill House is now part of the National Trust property of Downhill Demesne and Mussenden Temple.