Congratulatory messages from around the world poured in as Prince William's wife Kate Middleton gave birth to a baby boy, with Britons and the Royal family ecstatic at the arrival of Britain's future King.
The 31-year-old Duchess of Cambridge gave birth to a baby boy Monday evening at 16:24 (local time) at the private Lindo wing at St Mary's Hospital in Paddington, central London.
The fountain in Trafalgar Square was lit up with blue lighting to mark the birth of the third in line to Britain's throne and "It's a boy" was instantly being flashed on the BT Tower in central London.
In an official announcement, Buckingham Palace said, "The Queen and Prince Philip are delighted at the news of the birth of the Duke and Duchess of Cambridge's baby."
Queen Elizabeth II is expected to have been the first to be informed about her newest great-grandson by phone.
Prince Charles, the grandfather of the 8lbs 6oz boy, responded to news of the birth by saying he was "enormously proud and happy" of becoming a grandparent.
"Both my wife and I are overjoyed at the arrival of my first grandchild. It is an incredibly special moment for William and Catherine and we are so thrilled for them on the birth of their baby boy," he said.
"Grandparenthood is a unique moment in anyone's life, as countless kind people have told me in recent months, so I am enormously proud and happy to be a grandfather for the first time and we are eagerly looking forward to seeing the baby in the near future," Charles said.
British Prime Minister David Cameron was among the first to take to Twitter to say: "I'm delighted for the Duke and Duchess now their son has been born. The whole country will celebrate. They'll make wonderful parents".
The statement issued by Kensington Palace, the Duke and Duchess' official residence, confirmed that William was present for the birth.
"The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, Prince Harry and members of both families have been informed and are delighted with the news," the statement said.
US President Barack Obama and lawmakers congratulated the royal family on the birth of the new prince.
"Michelle and I are so pleased to congratulate The Duke and Duchess of Cambridge on the joyous occasion of the birth of their first child. We wish them all the happiness and blessings parenthood brings," he said.
"The child enters the world at a time of promise and opportunity for our two nations," Obama said in a statement.
Top-selling British newspaper 'The Sun' changed its name in Tuesday's edition to "The Son" to honour the royal baby.
Others like The Daily Telegraph, The Daily Star and The Daily Express splashed the headline "It's a Boy" across front-page photographs of the new mother.
Deputy Prime Minister Nick Clegg said, "the arrival of a first child is a very special time and we send our very best wishes to The Duke and Duchess of Cambridge - and indeed to all couples who have become proud parents on this very special day."
Opposition Labour leader Ed Miliband, writing on Twitter, said: "Many congratulations to the Duke and Duchess of Cambridge. I wish them and their son all happiness and good health".
In keeping with Britain's royal tradition, the news has now been posted on a framed notice on an easel at the front of Buckingham Palace, which was taken from the hospital by car by royal aides.
It reads: "Her Royal Highness the Duchess of Cambridge was safely delivered of a son at 4.24pm today. Her Royal Highness and her child are both doing well".
On the steps of the Lindo wing at St Mary's hospital, a town crier in colourful garb read out the news to the crowds.
Kate is likely to pose for the official photograph with her husband and the new baby boy on being discharged on Tuesday.
Australian Prime Minister Kevin Rudd said, "I think all Australians at the bottom of their hearts wish the royal bub all the best, and certainly wish the new parents all the best as well. This is a day of great joy."
In his message, Canadian Prime Minister Stephen Harper said, "The arrival of the newest member of the Royal Family, a future sovereign of Canada, is a highly-anticipated moment for Canadians given the special and warm relationship that we share with our Royal Family.
"This new beginning reminds us of the remarkable and enduring relationship our country has enjoyed with generations of the Royal Family."