Prince William's wife Kate gave birth to a baby boy on Monday, their first child who will be third in line to the British throne, ending hours of fevered anticipation outside the London hospital where the child was delivered.
The baby was born with William at Kate's side at 4:24 p.m. (11:24 ET) and weighed 8lbs 6oz (3.8 kg).
"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," Clarence House, Prince William's office, said in a statement.
"Her Royal Highness and her child are both doing well and will remain in hospital overnight."
The boy's name will be announced in due course, the statement said but bookmakers make George the favorite name, followed by James.
As the birth was announced, a loud cheer went up from the well-wishers and media gathered outside St. Mary's Hospital in west London, where William was born to the late Princess Diana in 1982.
"Both my wife and I are overjoyed at the arrival of my first grandchild," Prince Charles, William's father and heir to the throne, in a statement.
"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 he was enormously proud and happy to be a grandfather for the first time.
"We are eagerly looking forward to seeing the baby in the near future," he added.
The statement from Clarence House preceded the traditional announcement which saw an envelope containing the baby's details taken from the hospital to Queen Elizabeth's London residence, Buckingham Palace.
Aides then posted the information on a gold-colored easel outside the main gates.
The royal couple, officially known as the Duke and Duchess of Cambridge, had arrived at the hospital shortly before 6 a.m. and entered through a back door to avoid media camped outside the main entrance.
Kate and William, both aged 31, met when they were students at St. Andrews University and were married in April 2011 in a spectacular wedding broadcast around the world.
The royal birth has provoked a similar frenzy, with national and international media keeping up a deluge of speculative reports throughout Monday from outside the hospital.
Crowds gathered outside the hospital and Buckingham Palace, eager to hear news of the birth.
"Right across the country and indeed right across the Commonwealth people will be celebrating and wishing the royal couple well," Prime Minister David Cameron told waiting reporters in Downing Street.
"It is an important moment in the life of our nation but I suppose above all it's a wonderful moment for a warm and loving couple who got a brand new baby boy. It's been a remarkable few years for our royal family."
The baby arrives at a time when the royal family is riding a wave of popularity. An Ipsos Mori poll last week showed 77 percent of Britons were in favor of remaining a monarchy over a republic, close to its best-ever level of support.