Volodymyr Zelenskyy was among the foreign leaders to pay tribute to the Queen following her death aged 96.
The Ukrainian president joined the likes of US president Joe Biden and French leader Emmanuel Macron in offering their condolences.
Writing on Twitter, Zelenskyy said: “It is with deep sadness that we learned of the death of Her Majesty Queen Elizabeth II.
“On behalf of the Ukrainian people, we extend sincere condolences to the entire United Kingdom and the Commonwealth over this irreparable loss. Our thoughts and prayers are with you.”
Biden said the Queen had been “a stateswoman of unmatched dignity and constancy” who “helped make our relationship special”.
He added: “In the years ahead, we look forward to continuing a close friendship with The King and The Queen Consort.
“Today, the thoughts and prayers of people all across the United States are with the people of the United Kingdom and the Commonwealth in their grief.
“We send our deepest condolences to the Royal Family, who are not only mourning their Queen, but their dear mother, grandmother, and great-grandmother.
“Her legacy will loom large in the pages of British history, and in the story of our world.”
French president Macron said the Queen “embodied the British nation’s continuity and unity for over 70 years”.
He added: “I remember her as a friend of France, a kind-hearted queen who has left a lasting impression on her country and her century.”
Justine Trudeau, Canada’s prime minister, tweeted: “It was with the heaviest of hearts that we learned of the passing of Canada’s longest-reigning Sovereign, Her Majesty Queen Elizabeth II.
“She was a constant presence in our lives – and her service to Canadians will forever remain an important part of our country’s history.
“As we look back at her life and her reign that spanned so many decades, Canadians will always remember and cherish Her Majesty’s wisdom, compassion, and warmth.
“Our thoughts are with the members of the Royal Family during this most difficult time.”
Maltese leader Robert Abela said his country “joins the rest of the world in mourning the death of HM The Queen Elizabeth II”.
“As monarch and Head of the Commonwealth, she was loved by all. We will always remember her fondly, especially living here as a young princess. My condolences to the Royal Family.”
In a statement issued this afternoon, Buckingham Palace confirmed that the Queen died “peacefully” at Balmoral.
She has already been succeeded as monarch by her son, who will be known as King Charles III.
Speaking on the steps of Downing Street, new prime minister Liz Truss said: “We offer him our loyalty and devotion, just as his mother devoted so much, to so many, for so long.
“And with the passing of the second Elizabethan age, we usher in a new era in the magnificent history of our great country, exactly as Her Majesty would have wished, by saying the words ‘God save the King’.”