Chancellor George Osborne, US President Barack Obama, and author Oscar Wilde are among a host of public figures whose Irish ancestry has been revealed by an online database.
The predecessors of Walt Disney, CS Lewis and John F Kennedy also feature in the updated online collection of 19th century historical Irish records, which has been published ahead of St Patrick's Day on Thursday.
Mr Osborne is heir to the Osborne baronetcy of Ballentaylor. His great great great grandfather, Sir Henry Osborne, can be found in the Tithe Applotment Books, living in County Tipperary in 1824.
The Tithes feature more than 600,000 Irish land tax records, one of which relates to Mr Obama's great great great great grandfather who was living in Ballygurleen, Tipperary, in 1829.
More than a quarter of US presidents have claimed Irish roots, including JFK whose great great grandfather Patrick Kennedy lived in Wexford.
His name is found in Griffith's Valuation of Ireland, 1848-1864, which features more than 2.5 million names and addresses in land tax records. The records cover the critical period around the Irish Potato Famine and are especially valuable as a substitute for 19th century censuses of Ireland, most of which were destroyed during the civil war.
Griffith's also shows William Wilde, father of Oscar Wilde, living at Westland Row, Dublin, where the author was born in 1854.
The website's international content director Dan Jones said: "The new collections will be hugely relevant to anyone with Irish ancestry as they may hold the earliest or final record of their ancestors' existence during these tragic yet nation-defining years in Ireland's history.
"The Irish Potato Famine was a significant event in world history which caused a huge spike in international emigration from across Ireland - meaning today, people from every corner of the globe may find they have Irish ancestry."
In an ICM poll of 2,000 UK adults carried out to coincide with St Patrick's Day, one in five people said they had Irish ancestry. But the survey found only 15% of people were able to name the Irish capital city.