Queen Elizabeth II has died at the age of 96, Buckingham Palace has announced.
Her eldest son, Charles, is now King.
The Palace released a statement just after 6.30pm, local time, on Thursday, confirming her death.
“The Queen died peacefully at Balmoral this afternoon,” it read.
“The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow.”
Charles, who will be known as King Charles III, issued a statement saying the death of his “beloved mother” was a “moment of the greatest sadness for me and all members of my family.”
“I know her loss will be deeply felt throughout the country, the Realms and the Commonwealth, and by countless people around the world.”
Britain’s Prime Minister Liz Truss, who the Queen appointed to the role on Tuesday, said the former monarch was “the rock on which modern Britain was built.”
Greece has also joined the growing number of tributes to the Queen.
Greek Prime Minister, Kyriakos Mitsotakis, wrote on Twitter he was “deeply saddened” by her passing.
“The duty, service and dedication she demonstrated throughout her reign was not just exemplary but extraordinary,” Mitsotakis wrote.
Greece’s President, Katerina Sakellaropoulou, also marked Queen Elizabeth’s death on Twitter.
“Queen Elizabeth’s reign has marked the modern history of the United Kingdom. She has been a true pillar of her country and has been rewarded with love and respect,” Sakellaropoulou wrote.
“My heartfelt condolences to her family and the British people. She will be missed.”
In Australia, Prime Minister Anthony Albanese also issued a statement this morning and offered his condolences to the Royal Family.
“Today marks the end of an era, the close of the second Elizabethan age. This time of mourning will pass but the deep respect and warm regard in which Australians always held Her Majesty will never fade,” Mr Albanese said.
This morning, Archbishop Makarios of Australia expressed his sadness at the passing of Queen Elizabeth and expressed his hopes for King Charles.
“We are confident that the heir to the throne, King Charles, will honourably continue along the same path as that of late Queen Elizabeth,” Archbishop Makarios’ statement read.
The Queen’s body is expected to be taken from her estate at Balmoral, in north-east Scotland, to Edinburgh on Friday morning local time.
Her body is then expected to be taken to Buckingham Palace’s throne room before lying in state for four days in Westminster Hall.
The UK is expected to declare a period of national mourning ahead of the Queen’s funeral, which protocol says will be held at Westminster Abbey in London.