Actor Tom Cruise has said proof of his Irish roots is a great honour for him and his family.
In Dublin for the premiere of his latest blockbuster Oblivion, the Hollywood star was shown research that traces his heritage back to 12th century Norman knights.
Researchers also described one of his ancestors as a "hero landlord" after records showed he restored evicted tenants to lands just before the famine in Ireland.
Cruise said he had been taken aback by the depth of his family history.
"To learn about the history of my family - it was incredible," he said.
"I knew I was Irish but I had no idea where it went and the depth of it. It goes all the way back to the 12th century."
The star added: "It's a great honour for me and for my whole family - I can't wait to bring it back to them and enlighten them on their history.
"I'm very proud to be Irish. There's a pride in America of being Irish. I can't wait to come back and I want to visit the land of my ancestors and the castle that they had."
Cruise also had engagements with the Irish Film Board, a pre-recorded Late Late Show interview and a visit to the Guinness brewery during his whistlestop visit which began when Tanaiste and Foreign Affairs Minister Eamon Gilmore presented the star with a framed certificate of his Irishness at Iveagh House.
Genealogists, commissioned by Tourism Ireland on behalf of The Gathering - an initiative to attract the Irish diaspora to visit Ireland through 2013 - revealed the extent of the stars' Irish links.
The Hollwood A-lister, remembered for a cringing Irish accent in the 1992 film Far And Away, was a direct descendant of landlord Patrick Russell Cruise.
His great-great-great grandfather returned from America to Ireland after his land agent forced families from farms in Co Westmeath in 1843.
The landlord restored tenants to 500 acres around the townlands in Paristown and Dardistown in the years before the Great Famine when potato crops repeatedly failed.
Cruise was born Tom Cruise Mapathor IV in 1962.
The research showed that the Cruise and Mapathor families had settled in Ireland, with roots going back 800 years while a third family, the Russells, were also prominent in Cruise's ancestry.
The Cruises can trace their presence in Ireland back to the Anglo-Normans and Strongbow, Richard de Clare, earl of Pembroke and lord of Leinster.
In 1176 Augustino de Cruce, one of Strongbow's knights, acted as a legal witness to a grant by Strongbow of lands in Dublin.
The Cruises and the Russells were old English families who refused to conform to the Protestant faith and lost their lands in Ireland when they rebelled against Oliver Cromwell.
The families were united by marriage in 1766 and all subsequent relations including Patrick Russell Cruise had the double-barrelled surname.
The landlord was himself honoured publicly for his compassion for farmers on his land when a dinner was held in the town of Clonmellon in November 1844.
He died in Dublin in March 1849 without returning to America and was buried in Donabate, north Dublin. Other ancestors include Cruise's paternal great-great-grandmother Mary Pauline Russell-Cruise and his great-great grandfather Dillon Henry Mapother whose family were from Kilteevan, Co Roscommon.
The Mapothers were Elizabethan settlers originally from Dorset, England. Dillon Henry Mapother moved to Louisville, Kentucky, and on his death Mary Pauline married an Irishman called Thomas O'Mara and the couple had a son called Thomas O'Mara Junior.
On the death of Thomas Senior, his son took the name of his mother Cruise and his half-brother, Cruise Mapother, becoming Thomas Cruise Mapother I.
A-lister Tom Cruise is his great-grandson and the fourth member of the family to carry the name.
Later, Cruise - who is renowned for his dedication to his fans - lived up to his reputation at the Oblivion premiere.
The star spent more than an hour on the red carpet outside the Savoy Cinema on Dublin's O'Connell Street, signing autographs and posing for pictures with his adoring public.
Thousands of fans had braved the cold and lined the busy city centre street for hours waiting to catch a glimpse of the actor, now an honorary Irishman.
Cruise said he was fascinated to learn of his heritage, which had come as a huge surprise.
He even tried his hand at speaking some Irish.
"After I got my heritage I had to go pull myself a pint of Guinness, it was a lot of fun," he added.
The star said he was looking forward to audiences seeing his new movie, saying he was really pleased with it.
He added that he would also consider shooting a film in Ireland in the future.
"I don't have any production here but I'd like to shoot something here, it would be lovely," Cruise said.
"We don't have the film script, we don't have locations yet, but we shot here for Far and Away and it was such a great experience."
The star also paid tribute to Ireland's large talent pool of actors, film makers, directors and writers.
"I like how this country really supports their artists, its important. It makes this place very special," he said.