One of Ireland's most famous and celebrated actors, Richard Harris died in London after a battle with Hodgkin's Disease aged 72. The Taoiseach, Mr Ahern, led the tributes to the Limerick-born actor.
Mr Ahern said he was deeply saddened by the news and described Harris as "one of Ireland's most outstanding artists".
"I wish to extend my sympathy to his family and wide circle of friends," he said in a late night statement.
Harris died at University College Hospital in London at around 7 p.m. a spokesman for the family said. He had been receiving treatment for Hodgkin's Disease at the hospital after falling ill earlier this year.
The spokesman said: "With great sadness, Damian, Jarid and Jamie Harris announced the death of their beloved father Richard Harris.
"He died peacefully at University College Hospital, London, at 7pm today."
The Irish-born actor starred in Gladiator, Unforgiven, and This Sporting Life, but he'd become known to a new generation of film fans through his role as Professor Albus Dumbledore in Harry Potter and the Philosopher's Stone.
He had just completed work on the new film, Chamber of Secrets, before falling ill this summer.
He starred in some of the classic films of his generation, including A Man Called Horse, The Guns of Navaroneand Mutiny on the Bounty, but was prone to fill the columns of tabloid newspapers with his wild ways and hard-drinking exploits.
He was twice bankrupted, divorced, and underwent a reformation and acting resurrection in the early 1980s, when told he had only 18 months to live if he did not stop drinking.
He responded by buying the rights to the stage production of Camelot and toured the world with it for five years, becoming a multi-millionaire in the process.
Film director Michael Winner said: "The lights have dimmed a lot with his passing. He was my neighbour for 10 years, and he was the most wonderful, warm character.
"He was not only a great friend and a very wonderful person to be with, he was one of our greatest actors, and had this great charisma of the star, which extended to his private life. He was the archetypal star, he was like an old Hollywood legend."
British chat show host Michael Parkinson said: "He was an extraordinary man, a great storyteller, very intelligent."
Parkinson, who interviewed Harris three times, added: "He was a hellraiser - it's a cliche, but that's what he was. He was from the old school of stars, like Peter O'Toole, strolling players, guys who love life."
Harris hoped to be in the third Harry Potter film, Harry Potter and the Prisoner of Azkaban, which starts shooting in March. Director Chris Columbus said before the actor's death was announced: "He did threaten to kill me if I recast him - I can't even repeat what he said to me."
PA