Tributes to Queen Elizabeth II have been paid from leaders in Ireland and around the world.
President Michael D Higgins said her visit to Ireland in 2011 was pivotal in laying a firm basis for an understanding between Ireland and the United Kingdom.
Taoiseach Micheál Martin said Queen Elizabeth made an enormous contribution to strengthening relations between the two countries.
A Book of Condolence will be opened at the British Embassy in Dublin today for people to pay their respects.
Outside of the UK, Queen Elizabeth was head of state of 14 other countries, including Australia, Canada and Jamaica.
Canadian Prime Minister Justin Trudeau said Elizabeth was a "constant presence in our lives - and her service to Canadians will forever remain an important part of our country's history".
Australian Prime Minister Anthony Albanese paid tribute to her "timeless decency" and said her death marked the "end of an era".
The smallest Commonwealth members also paid tribute, with David Burt, premier of tiny British territory Bermuda, hailing her "life of undimmed duty".
South Asia, where Britain was the colonial power until just before Elizabeth's reign began, paved the way, with India's Prime Minister Narendra Modi saying he was "pained" by her death.
South African President Cyril Ramaphosa described how he and the queen had reminisced together about Nelson Mandela, while Kenya's president-elect William Ruto hailed her "admirable" leadership of the Commonwealth.
Outgoing Kenyan President Uhuru Kenyatta expressed his "deep sense of loss" at the queen's passing.
"Her Majesty Queen Elizabeth II was a towering icon of selfless service to humanity and a key figurehead of not only the United Kingdom and the Commonwealth of Nations where Kenya is a distinguished member but the entire world," he said in a statement.
Mr Kenyatta said he "received the sad news... with great sorrow and a deep sense of loss", noting the former British colony's close ties with the queen.
'Unmatched dignity and constancy'
US President Joe Biden called the queen the first British monarch to make a personal connection with people around the world, as he ordered flags at the White House and government buildings flown at half-staff in her honor.
"Queen Elizabeth II was a stateswoman of unmatched dignity and constancy who deepened the bedrock alliance between the United Kingdom and the United States. She helped make our relationship special," he said.
Others who have taken a less friendly view of Britain also sent tributes.
Russian President Vladimir Putin offered his condolences to King Charles III, wishing the new monarch "courage and resilience" after his mother's death - even as Britain leads the West in imposing sanctions on Moscow over its invasion of Ukraine.
His spokesperson Dmitry Peskov said Mr Putin is not planning on attending the funeral.
Chinese President Xi Jinping gave his "sincere sympathies to the British government and people" following the death of Queen Elizabeth II.
While Germany, which in the queen's lifetime went from Britain's greatest enemy to a powerful ally, hailed her as a "symbol of reconciliation" after two world wars.
"Her commitment to German-British reconciliation after the horrors of World War II will remain unforgotten," said German Chancellor Olaf Scholz.
Japanese Prime Minister Fumio Kishida echoed that sentiment.
"She played a significant role in creating world peace and prosperity," Mr Kishida said, adding the queen's death was a "big loss" to the international community.
Japan's Emperor Naruhito hailed Queen Elizabeth's "many achievements and contributions", saying he felt "deep sorrow" at news of her death.
"I express my heartfelt respect and gratitude to the Queen for the many achievements and contributions she has made," he said in a statement issued by the Imperial Household Agency.
Argentina, which fought and lost a bitter war with Britain over the Falkland Islands in 1982, expressed its "regret" over Elizabeth's passing.
In a terse statement from the foreign ministry, the government offered its sorrow and said it "accompanies the British people and her family in this moment of grief".
'Grace, dignity, and dedication'
At the United Nations, the Security Council held a minute of silence.
Queen Elizabeth had been "widely admired for her grace, dignity and dedication around the world. She was a reassuring presence throughout decades of sweeping change," UN Secretary-General Antonio Guterres said.
In the Vatican, Pope Francis said he was "deeply saddened" by her death and would pray for the late queen as well as King Charles.
European Union leaders expressed regret at the death of the queen, who was Britain's head of state throughout its entire EU membership and eventual departure.
"Once called 'Elizabeth the Steadfast', she never failed to show us the importance of lasting values in a modern world," said EU council president Charles Michel.
Philippe, king of the Belgians, who has a close family link to the British aristocracy, hailed the queen as "an extraordinary personality".
King Carl XVI Gustaf of Sweden called her "a good friend of my family and a link to our common family history".
Spanish King Felipe VI said she "wrote the most relevant chapters of history".
And Saudi King Salman noted that "Her Majesty was a model of leadership that will be immortalised in ... history".
Scottish leader Nicola Sturgeon, who supports Scotland's independence from the rest of Britain, called her death "a profoundly sad moment for the UK, the Commonwealth and the world".
French President Emmanuel Macron hailed the queen as "a friend of France... who marked her country and her century as never before".
Far-right President Jair Bolsonaro of Brazil, which does not have particularly close ties to Britain, paid homage. Mr Bolsonaro, seeking re-election next month, declared three days of national mourning and called Elizabeth "a queen not just to Britons, but to all of us".
Visit to Ireland
EU Special Representative for Human Rights and former leader of the Labour Party Eamon Gilmore this morning recalled the queen as someone who was "warm and engaging".
He was Tánaiste in the 2011 coalition government during her State visit to Ireland.
He said: "My memory of her was someone warm, engaging and very happy to be in Ireland."
It was an important journey for her to visit the Garden of Remembrance, paying respect to the people who had fought against the British, building Irish-British relations.
He said her use of Irish was perfect at Dublin Castle. "It was this message that looking back, the benefit of hindsight. It was a very strong message."
Mr Gilmore said she did a lot for reconciliation. He said he had the opportunity to meet the queen on other occasions after this initial encounter in 2011 and she spoke constantly about her visit to Ireland, and particularly Cork.
The people and streets of Cork left an impact, he added.
