The Hon. Desmond Walter Guinness (born 8 September 1931) is an Irish author on Georgian art and architecture and a conservationist. He was the second son of the author and brewer Bryan Guinness, 2nd Baron Moyne and Diana Mitford (later Lady Mosley). He was educated at Eton, Gordonstoun and Christ Church, Oxford.
In 1958 he bought Leixlip Castle, Leixlip, County Kildare, Ireland, where he continues to live with his second wife, the former Penelope Cuthbertson, whom he married in 1984. As a member of the extended Guinness family he has a number of well-known relatives, such as Garech Browne. He has been Master of the North Kildare Harriers.
Irish Georgian Society
He and his first wife, Mariga (the former Princess Marie Gabrielle of Urach), founded the Irish Georgian Society in April 1958 to help to preserve Irish architecture of all periods. This was timely as the Irish planning laws were enacted only from 1963.
The IGS became involved in numerous projects and started publishing quarterly bulletins. Some early preservations or campaigns were at: Damer House (Tipperary), The Conolly Folly (Kildare), Mountjoy Square, Tailors' Hall, Hume Street (Dublin) and the Dromana Gateway, (Waterford).
The IGS also held Georgian cricket matches played to the rules of 1744.
His conservation work has been recognised by many American and English cultural groups, and Europa Nostra. In 1980 he was made an honorary Doctor of Laws at Trinity College Dublin. In 2001 he was made an honorary member of the Royal Institute of the Architects of Ireland and was awarded the gold medal of the Eire Society of Boston. In 2006 he was presented with a Europa Nostra award by the Queen of Spain. In 2010 he headed the Saint Patrick's Day parade in Seattle. In June 2014 he was awarded an honorary lifetime membership of the Royal Dublin Society.
Married at Oxford in 1954 to Princess Henriette Marie-Gabrielle ("Mariga") von Urach, daughter of Prince Albrecht von Urach and a granddaughter of King Mindaugas II of Lithuania, by whom he had a son, Patrick Desmond Carl-Alexander, and a daughter, Marina. Through Patrick he is a grandfather of the fashion model Jasmine Guinness. His daughter Marina is a patron of the arts and of Irish musicians including Glen Hansard, Damien Rice, and the band Kíla. Marina has three children of her own: Patrick (by Stewart Copeland of The Police), Violet (by photographer Perry Ogden), and Finbar (by record producer Denny Cordell). 
- Portrait of Dublin (New York, Viking Press, 1967)
- Georgian Dublin (Batsford, B.T., Ltd.1979) ISBN 978-0-7134-1908-5
Three books with Julius Trousdale Sadler:
- Mr Jefferson, architect (New York, Viking, 1973) ISBN 978-0-670-49261-9
- Palladio: A Western Progress (New York, 1976) ISBN 978-0-670-53732-7
- Newport preserv'd : architecture of the 18th century (New York : Viking Press, 1982) ISBN 978-0-670-50938-6
With William Ryan:
- Irish Houses and Castles; with William Ryan. (London: Thames & Hudson 1973).
- The White House: An Architectural History (New York: McGraw-Hill, 1980). ISBN 978-0-07-054352-2
With Jacqueline O'Brien, wife of the famous racehorse trainer Vincent O’Brien:
- Dublin – A Grand Tour (Weidenfeld & Nicholson 1994)
- Great Irish Houses and Castles (Harry N. Abrams, Inc.) ISBN 978-0-8109-3365-1 (December 1998) and in paperback (Weidenfeld & Nicolson September 1993) ISBN 978-0-297-83236-2.
He has also written numerous articles such as: Thomas Jefferson: Visionary Architect. Horizon, 22 (1979): 51–55.
- Address on the award to Desmond Guinness of the European Union Prize for Dedicated Service to Heritage Conservation Irish govt. 2007.
- The peerage.com
- Hon. Desmond Walter Guinness (thepeerage.com)
- Archiseek.com 404 Error
- Castletown House, Co Kildare (Alessandro Galilei & Edward Lovett Pearce) – Irish Architecture
- http://www.heritageireland.ie/en/HistoricSites/East/CastletownKildare/ Archived 23 November 2007 at the Wayback Machine.
- Contemporary and Historical Irish Architecture and Architects – Archeire – Irish Architecture Online
- http://www.igs/publications/2005_spring.pdf[dead link]
- Parade Grand Marshals
- Irish Times, 27 June 2014
- Jasmine Guinness, Fashion model
- Bohemian rhapsody: Marina Guinness and Kila | 2008
-  Archived 8 November 2005 at the Wayback Machine.
- Obituary: Zita Jungman | News | The Guardian
- CKAS homepage
- Motorsport Ireland :: RIAC Archive Archived 6 September 2006 at the Wayback Machine.