Coordinates: 54°11′13″N 6°22′41″W / 54.187°N 6.378°W Derrymore House is a National Trust property in Bessbrook, County Armagh, Northern Ireland. It is open to the public and is described by the National Trust as a "late 18th-century thatched house in gentrified vernacular style".
Built in the style of a cottage orné, house is set in over 100 acres (0.40 km2) of beautiful parkland and woodland. It features unique local thatching using Shannon reeds.
It was built between 1776 and 1787 by Isaac Corry, MP for Newry for thirty years, on land he inherited from his father. The house was described by Sir Charles Coote as "without exception, the most elegant summer lodge..." The Act of Union was drafted in the drawing room (now known as the Treaty Room) of the house in 1800. The surrounding parkland was laid out by John Sutherland, one of the most celebrated disciples of Capability Brown.
Derrymore was sold by Corry in 1810, when he moved to Dublin, and was later acquired by the Young family. Sir William Young, Bart. sold the Derrymore estate in 1825 to the Smyth family. The demesne, which hosted 140,000 trees, was then bought by a wealthy Merchant Robert Glenny of Trevor Hill in Newry who in turn sold it onto the linen manufacturer John Grubb Richardson who lived in the adjoining estate, The Woodhouse. Richardson was responsible for establishing the village of Bessbrook, and building Bessbrook Friends' Meeting House, which sits in the Derrymore demesne. In 1952 Mr. J. S. W. Richardson, a descendant of J. Grubb Richardson, donated Derrymore House and his estate at Bessbrook to the National Trust. The National Trust subsequently undertook to demolish a large portion of the house, which had been added by the Richardson family in the Georgian style, in order to return the property to the manner in which Isaac Corry had known it.