Monreith House is a category A listed Georgian mansion located 1.5 kilometres (0.93 mi) east of the village of Port William in Mochrum parish in the historical county of Wigtownshire in Dumfries and Galloway, Scotland.

Magdalene Blair, wife of the third baronet, made tapestries of the gardens in the mid 17th century, which remain in the house.

[2] Sir William Maxwell, 4th Baronet, inherited the estate in 1771 and commissioned the present Monreith House from Alexander Stevens (1739–1796) in 1791.

His grandson was Gavin Maxwell author of Ring of Bright Water, who was born at The House of Elrig on the estate.

Gavin's older brother, Sir Aymer Maxwell, the 8th Baronet, owned the house and estate at this point, although was forced to sell the Maxwells' farming interests to a consortium of local businessmen in the 1950s, only retaining ownership of the house and its grounds.