Newton House is a Grade II* listed country house situated just to the west of the market town of Llandeilo in Carmarthenshire, Wales. It is owned and maintained by the National Trust and lies within Dinefwr Park and the grounds of Dinefwr Castle. The original house was built during the Medieval period on a site which has been occupied for at least two millennia. The current house was built by Edward Rice in the Jacobean style in 1660, though extensive changes were made in the 1850s in the Venetian Gothic style. The house played a role in the Rebecca Riots of 1843, when the occupant of the house at the time, Colonel George Rice, received a death threat with an empty grave dug in the ground. After 1956 the property fell into turbulent times when two owners died within the space of a few years. It was sold in 1974, and later fell into disrepair; it was occupied by squatters and thieves who removed beams and furniture.
The house, along with Dinefwr Castle, have since been restored by the National Trust and Cadw respectively. It is a three-storey castellated structure, built from grey stone, with four tall towers in each corner, with sloping slate roofs. The front features a grand central porch. Two rooms are open to the public, including a tearoom and exhibition in the basement and ground floor which contain numerous displays related to the history of the estate and occupants. The deer park which surrounds the property was landscaped by Capability Brown in 1775. The surrounding woodland consists mainly of oak and wych elm. Newton House is cited as one of the most haunted houses in Wales, noted in particular for its ghost of Walter the Butler, a former employee whose tobacco smoke purportedly wafts through the air.