Patrick Desmond Carl Alexander Guinness, KCEG KLJ (born 1 August 1956 in ) is an Irish historian and author, one of heirs of the Guinness business dynasty, and additionally the rightful heir of several medieval-originated honours and titles which he has not claimed openly. Son of Desmond Guinness and Marie-Gabrielle von Urach, he was educated at Winchester College and . He continues his father's business in real estate development and is a financial analyst. He formerly represented Sotheby's in Ireland. Historian A historian, Patrick Guinness has authored the first biography of Arthur Guinness, the founder of the dynasty. Patrick has lectured on genetic genealogy relating to the early Irish dynasties and Viking Ireland, and has sponsored academic research on Irish genetics. He was a council member of the County Archaeological Society (2004–14)and of the Order of Clans of Ireland.

Patrick has produced monographs on the early history of the Friendly Brothers of St Patrick in Kildare, 1758–91; on the depositions from Kildare on the outbreak of the Irish Rebellion of 1641;[7] and on the Irish Jacobite ancestry of the Mitford family (privately published). Family His daughter by his first marriage is model Jasmine Guinness. He remarried in 1990 to Louise Arundel; the couple has four children. Through his mother's grandfather William, second Duke of Urach, he is a potential claimant to the medieval Kingdom of Jerusalem, the Kingdom of Lithuania and to the Principality of Monaco (see Monaco Succession Crisis of 1918). He is also 2259th in line of succession to the British throne. In 2015 he gave a lecture on Irish history at the Princess Grace Irish Library in Monaco.

Patrick Guinness, eldest son of his late mother, is one of those persons living today who is genealogically legitimate heir general of several noble families at least as far as from the 15th century. These heirships include that of marquess Rodolphe de Bade, count of Neuchatel (1427-1487) and that of Adrienne d'Estouteville (1512-1560), in her own right heiress of Estouteville in Normandy, who was created 1st Duchess of Estouteville in the peerage of France.

Partly because of previous family involvements, he is a trustee of the Iveagh Trust social housing provider, and President of the Irish Georgian Society. Honours In September 2010, he became a Knight of Justice of the Military and Hospitaller Order of St. Lazarus of Jerusalem at a ceremony in St. Patrick's Cathedral in Dublin. In 2013, he was made a Knight Commander of the Order of the Eagle of Georgia by HRH Prince David Bagrationi Mukhran Batonishvili, Head of the Royal House of Georgia.

On 10 March 2015 the Texas Senate passed a resolution sponsored by Senator Watson welcoming Mr Guinness to the Texas State Capitol.