Belsay Castle is a 14th-century medieval castle situated at Belsay, Northumberland, England. It is a Scheduled Ancient Monument and a Grade I listed building.
The main structure, a substantial three story rectangular pele tower with rounded turrets and battlements was constructed about 1370, and was the home of the Middleton family. In 1614 Thomas Middleton built a new manor house attached to the tower. A west wing was added in 1711 but was later largely demolished in 1872 by Sir Arthur Middleton when the remainder of the house was considerably altered.
The castle was abandoned as a residence by the family in the early 19th century when Sir Charles Monck built Belsay Hall close by. It is administered by English Heritage and is open the public. The interiors were largely removed and it was then used as a ready-made folly, as was fashionable among the aristocracy at the time, serving as setting for garden parties and other entertainments.
The house was built between 1810 and 1817 for Sir Charles Monck (then of Belsay Castle close by) to a design by architect John Dobson. It is built in ashlar with a Lakeland slate roof in the Greek Doric style.
The house measures 100 feet (30 m) square with a lower kitchen wing attached to the north side. Externally the house appears to have two stories,although there is an additional storey hidden within the roof space to house servants etc.
This service side of the house was badly affected by dry rot in the 1970s and, following remedial work, it has been left as a weather-proof shell to illustrate how the house was built. The hall was the residence of the Middleton family until 1962.