Russborough House is a stately house situated near the Blessington Lakes in County Wicklow, Ireland, between the towns of Blessington and Ballymore Eustace and is reputed to be the longest house in Ireland, with a frontage measuring 210 m/700 ft. It is an example of Palladian architecture, designed by Richard Cassels for Joseph Leeson, 1st Earl of Milltown and built between 1741 and 1755. The interior of the house contains some ornate plasterwork on the ceilings by the Lafranchini brothers, who also collaborated with Cassels on Carton House.
Russborough has housed two fine art collections, begun with the Milltown estate, whose collection was donated to the National Gallery of Ireland by the widow of the sixth earl.
Sir Alfred Beit bought the house in 1952 where he housed his own family's collection, comprising works by many great artists, including Goya, Vermeer, Peter Paul Rubens and Thomas Gainsborough. This collection was since robbed four times, in 1974 by an IRA gang including British heiress Rose Dugdale, in 1986 by Martin Cahill (nicknamed "The General"), in 2001, and in 2002 by Martin Cahill's old associate Martin Foley . Two paintings, Gainsborough's Madame Bacelli and Vermeer's Lady writing a Letter with her Maid, the latter probably the most valuable painting of the collection, were stolen twice across the thefts, although each was subsequently recovered. The Beit collection has donated many of its works to the state but substantial proportion of the paintings have been returned and been made available to view by the owners, the Alfred Beit Foundation.
Amongst the paintings returned are four Claude Joseph Vernet paintings entitled ‘Morning’ ‘Midday’ ‘Sunset’ and ‘Night’. These paintings were actually painted for Russborough in the 1750s and had remained in the house for most of the last 260 years. Vermeer's Lady Writing a Letter With Her Maid and Goya's Portrait of Dona Antonia Zarate were recovered in 1993.
The Leeson family originated in Northamptonshire and had moved to Ireland in the second half of the 17th century. A sizeable fortune made in brewing and property development in Dublin passed down to Joseph Leeson, who bought land at what was then Russelltown. He became an MP and was made Earl of Milltown in 1763. 
Russborough house was designed for Joseph Leeson by Richard Cassels and built between 1741 and 1755. It remained in the possession of the Earls of Milltown until the sixth earl. On the death of his widow in 1914 it passed to a nephew, Sir Edmund Turton, who rarely stayed there. On Turton's death in 1928, his widow sold the house to Captain Denis Bowes Daly in 1931. Sir Alfred and Lady Beit bought Russborough in 1952 from Captain Daly to house their art collection and in 1976 established the Alfred Beit Foundation to manage the property. The foundation opened the historic mansion and its collections to the Irish public in 1978. Beit died in 1994 but Lady Beit remained in residence until her own death in 2005. 
On February 7, 2010, a fire severely damaged the west wing and caused part of the roof to collapse. No art was damaged, being removed along with furniture to allow for restorations to the west wing. Initial examinations of the damage suggested an electrical fault from wiring in the roof may have sparked the fire.
In recent years locally advertised Farmers Markets have been held on a regular basis in the grounds of the house.
- Info from kildare.ie
- RTE: History of robberies in Russborough
- Dolnick, Edward (June 2005). The Rescue Artist. HarperCollins. ISBN 978-0-06-053117-1.