The Duke and Duchess of Cambridge have a son.
Kate gave birth to their baby boy at 4.24pm on July 22 at the Lindo Wing of St Mary's Hospital in Paddington.
The news was announced by Kensington Palace in a statement which read:
"Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 4.24pm.
"The baby weighs 8lbs 6oz.
"The Duke of Cambridge 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.
Her Royal Highness and her child are both doing well and will remain in hospital overnight."
Cheers erupted through the crowded street outside the private Lindo Wing and cries of 'It's a boy!' shortly after 8.31pm.
Ed Perkins, Press Secretary to Prince William, emerged from the Lindo wing a few minutes later with a wry smile on his face and a red leather folder in his hand.
He passed it through the window of a blue Jaguar car.
That notice giving details about the baby - the third-in-line to the throne after Prince Charles and Prince William - left was taken by car to Buckingham Palace.
It has been signed first by the Queen's former gynaecologist Marcus Setchell, who led the medical team that delivered Kate's baby.
The notice was placed on an ornate gold easel in the palace's forecourt by the Queen's press secretary Ailsa Anderson, a traditional element of theatre last used 31 years ago for the announcement of William's birth on June 21, 1982.
Prime Minister David Cameron stuck to the more modern Twitter with his tweet below.
The new royal baby will be the Queen's third great-grandchild. Peter Phillips has two daughters.
The Prince of Wales, a grandfather for the first time, released this statement shortly after the notice went up at Buckingham Palace:
"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.
"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."
Kensington Palace has said: "The names of the baby will be announced in due course."
Later another statement was issued from Prince William. He said simply: "We could not be happier."
At a St Patrick's Parade in March, the Duchess let slip that she would prefer a boy.
Kate was admitted to hospital around 5.30 am in the morning 'in the early stages of labour'.
So what do you thing the new Prince will be called?