The Duchess of Cambridge, wife of Britain's Prince William, gave birth her third royal baby, a boy, on Monday at St. Mary's Hospital in London.
The royal family announced made the announcement on Monday.
Kate Middleton was admitted to hospital in London after going into labour with her third child early on Monday morning.
The palace has now revealed she has given birth to a healthy son weighing 8lbs 7oz.
“Her Royal Highness The Duchess of Cambridge was safely delivered of a son," palace officials said in a statement.
“The baby weighs 8lbs 7oz. The Duke of Cambridge was present for the birth. Her Royal Highness and her child are both doing well.
“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.
"Her Royal Highness The Duchess of Cambridge was admitted to St. Mary’s Hospital, Paddington, London earlier this morning in the early stages of labour," Kensington Palace tweeted earlier in the day.
"The Duchess travelled by car from Kensington Palace to the Lindo Wing at St. Mary’s Hospital with The Duke of Cambridge."
It is likely the couple will pose for photos with their newborn son outside the Lindo Wing when they leave hospital - just as they did with their two previous children.
It is the same hospital where Prince George was born in 2013, and his younger sister, Princess Charlotte in 2015.
It is also the birthplace of their father Prince William and uncle Prince Harry.
The duchess went on maternity leave on 22 March, and parking restrictions notices and barriers were put in place in front of the Lindo Wing on 9 April.
The baby prince is fifth in line to the throne, the Queen and the Duke of Edinburgh’s sixth great-grandchild, and his title will be HRH Prince.
Now the baby has arrived, Prince Harry will shift down the line of succession to sixth place.
The newly-born baby will be behind his sister Prince Charlotte in the line of succession despite the fact he is a boy. This due to a change in the primogeniture laws.
The palace have said the name of the boy will be announced in due course.