The Duchess of Cambridge was hoping for a son and her wish has come true.
The baby weighed 8lbs 6oz and was born at 4.24pm.
And William, the Duke of Cambridge said simply: “We could not be happier.”
Well-wishers from around the globe screamed with excitement as news of the birth of the royal baby spread to Buckingham Palace.
One man shouted: “It’s a boy,” prompting crowds to erupt into spontaneous cheering, ahead of the easel being placed in the forecourt.
Three were three cheers of “hip hip hooray,” as the crowd outside the palace gates swelled to more than 10 deep.
A Buckingham Palace spokesman said: “The Queen and Duke of Edinburgh are delighted at the news.”
The Prince of Wales issued a brief statement: “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 thrilled for them.
“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.”
Moments before Charles’s joyous words were released the Queen’s press secretary Ailsa Anderson strode out onto Buckingham Palace’s forecourt to place the official notice on its ornate stand.
The document had four signatures, first was that of Marcus Setchell, Surgeon Gynaecologist to Queen, who led the medical team that delivered Kate’s baby.
Mr Setchell said “wonderful baby, beautiful baby” as he left the Lindo Wing at around 9.20pm alongside other members of the medical team.
Kensington Palace said “The names of the baby will be announced in due course.”
A smiling David Cameron declared the birth “an important moment in the life of our nation”.
The naming game
The Duke and Duchess of Cambridge are expected to pick a traditional royal name for their newborn baby Prince.
Royal infants mostly have historical names which are passed down through the generations.
Charles Kidd, editor of Debrett’s Peerage and Baronetage, predicted that William and Kate would select a conventional first name for their son.
“I do think that Prince William is quite a traditionalist - that’s my feeling,” Mr Kidd said.
“The fact that he chose to use the royal dukedom (of Cambridge) and has followed royal precedent, I wouldn’t be surprised if they use a name that is already familiar in the royal family - something that has royal associations.”
He suggested that George - a favourite at the bookmakers - could be their name of choice.
There are also predictions that the couple will honour William’s father the Prince of Wales by choosing Charles and the Duke of Edinburgh by selecting Philip. Midway through her pregnancy, Kate revealed she and William had a shortlist of names.
Congratulations Round Up
Messages of congratulations for the royal couple flooded in from around the globe.
But there were some peersonal messages they would have been pleased to receive. Oliver Hicks, 31, a close friend of Prince William, said he was thrilled to hear the “fantastic” announcement.
The adventurer said he had been hoping for news since completing the first recorded kayak crossing of the North Sea between Britain and Norway, on Friday.
“It’s just such fantastic news,” he said. “Presumably it’s also much easier that it’s a boy. I hope I’ll get to see him soon. I can’t wait to see all of them.”
Archbishop of Canterbury the Most Rev Justin Welby was one of the first to speak of his joy on Twitter.
“Delighted for the Duke and Duchess of Cambridge as they welcome their baby boy. May God bless them all with love, health and happiness,” he said.
Labour Leader Ed Miliband added: “Many congratulations to the Duke and Duchess of Cambridge. I wish them and their son all happiness and good health.”
Even former Spice Girl Emma Bunton expressed her excitement - echoing a sentiment felt among the hordes gathered outside Buckingham Palace.
“It’s a boy!!! Special times ahead for Kate and William,” she said. Foreign Secretary William Hague added: “My warmest congratulations to the Duke and Duchess of Cambridge.
“Wonderful news and a happy moment for our country.”
Canada’s prime minister Stephen Harper sent his “heartfelt congratulations” to the couple and the royal family on behalf of all Canadians.
Outgoing Chief Rabbi Lord Sacks tweeted “Mazal Tov”.