Prince Philip has died at the age 99, Buckingham Palace announced on Friday.
A tweet from the official royal family account confirmed the news, saying: "It is with deep sorrow that Her Majesty The Queen has announced the death of her beloved husband, His Royal Highness The Prince Philip, Duke of Edinburgh."
He "passed away peacefully" at Windsor Castle, the tweet said.
The Royal Family join with people around the world in mourning his loss.
Further announcements will be made in due course.
Visit https://t.co/utgjraQQv5 to read the announcement in full.â€” The Royal Family (@RoyalFamily) April 9, 2021
The Queen's husband had been admitted to hospital in February for a procedure to treat a pre-existing heart condition.
He was released from the hospital on March 16 and returned to Windsor Castle.
The Duke of Edinburgh married Elizabeth in 1947 before she ascended to the throne. He was born on the Greek island of Corfu in 1921 and was a member of the Greek royal family.
Philip retired from public engagements in 2017 after having carried out over 20,000 of them. He was the longest-serving consort in British history.
Downing Street lowered the flags to half-mast, footage circulated on social media platforms showed.
BREAKING: The flags in Downing Street have just been lowered to half-mast following the death of the Duke of Edinburgh. pic.twitter.com/xJY0Misl43â€” Daniel Hewitt (@DanielHewittITV) April 9, 2021
Kier Starmer, leader of the UK Labour Party expressed his condolences, saying that the UK had "lost an extraordinary public servant" in a tweet.
"Prince Philip dedicated his life to our country - from a distinguished career in the Royal Navy during the Second World War to his decades of service as the Duke of Edinburgh," said Starmer.
"However, he will be remembered most of all for his extraordinary commitment and devotion to The Queen. For more than seven decades, he has been at her side," he added.
This is a breaking news story and will be updated as more details become available.