President Michael D Higgins is leading tributes to Muhammad Ali here - saying many will remember the wit, grace and beauty he brought to boxing.
Mr Higgins says - as a sportsman and humanitarian - and as someone who struggled for a very long time with one of the most debilitating illnesses - he offered courage in the face of great difficulties.
In 1967 Ali refused to be drafted to fight in Vietnam - he was convicted, stripped of his world title and boxing licence.
Four years later he returned to the sport and fought Al Blue Lewis in Croke Park in 1972.
Olympic Gold medallist Michael Curruth says we'll never see his like again: “My own father suffered from Parkinsons prior to his own death as well so I kind of understand what Muhammad Ali was going through you know?
“This name will never be forgotten.”
Tributes have flooded in from the sports world and beyond for Muhammad Ali.
Former heavyweight boxing champion Evander Holyfield told MSNBC: "I'm glad to have known Ali because when I was a kid, at eight years old, I was told I would be like Ali.
"To take it upon yourself and say; 'I'm the greatest', you put yourself in a position for people to take pot shots at you. This is what Ali did. It's amazing him becoming three-time heavyweight champion of the world. At that time people thought, 'Who could beat three?
"You have to be stronger to get up from a loss to go on and that's what Ali proved to be."
Former England footballer Gary Lineker tweeted: "The greatest has fought his final round. Muhammad Ali was the most magnificent athlete who transcended his sport."
Argentinian boxer Marcos Maidana, a two-weight former world champion, tweeted: "Muhammad Ali the all-time greatest has left us. Thanks for everything. Go with God."
Musician Wyclef Jean wrote: "I am the greatest, I said that even before I knew I was. Rest in peace to the greatest @MuhammadAli #MuhammedAli we lost another legend."
British boxer Amir Khan tweeted: "Our Prayers and thoughts are with @MuhammadAli and his family #AliBomaye."
Former heavyweight champion Mike Tyson tweeted: "God came for his champion. So long great one. @MuhammadAli #TheGreatest #RIP."
Ali's former promoter Don King told CNN: "He's always been right there, Johnny on the spot, anything he could do for the benefit of mankind.
"Let us celebrate his life. This is not a time to mourn. This is a time to try to emanate the job he was doing and the burden he leaves behind for us to carry on, to remember that the people are the most important."
Boxing champion Floyd Mayweather Jr told Fox News: "There will never be another Muhammad Ali. The black community all around the world, black people all around the world, needed him. He was the voice for us. He's the voice for me to be where I'm at today.
"I just want to thank Muhammad Ali and his family for being such strong people. You will always be missed. My prayers go out to Ali and his family."
George Foreman, Ali's friend and rival from the famous "Rumble in the Jungle" fight, told the BBC: "We were like one guy - part of me is gone."
"Muhammad Ali was one of the greatest human beings I have ever met. No doubt he was one of the best people to have lived in this day and age.
"To put him as a boxer is an injustice."
He also spoke of Ali's love for the UK and the way he was treated in the country.
"He loved London. If he had been born and raised in London he never would have changed his name," he said.
Former boxing champion Oscar De La Hoya tweeted: "RIP @muhammadali, a legend who transcended sport and was a true champion for all. #thegreatest #MuhammadAli."
Boxing promoter Kellie Maloney told the BBC that Ali was an "icon".
She said: "He took boxing from the back pages, he made it a national sport. He made it well known to the world."
She told BBC 5 Live: "You either loved him or hated him, but what you did was respect him.
"He transcended boxing, took it to a new level. He was the first real superstar, not just in boxing but in sport.
"If you asked my daughters who the favourite sportsman in the world is, they'd say Muhammad Ali. He didn't just win battles in the ring, he won battles outside of the ring."
Maloney met Ali while at a function with her former fighter, Lennox Lewis, and added: "He could hold a room. Even when he wasn't well, people were in awe of him."
Tributes also came from figures outside the world of boxing.
Ringo Starr, who met the boxer along with the other members of The Beatles in 1964, tweeted: "God bless Muhammad Ali peace and love to all his family."
Prime Minister David Cameron tweeted: "Muhammad Ali was not just a champion in the ring - he was a champion of civil rights, and a role model for so many people