Kate Middleton has given birth to a girl at St Mary's Hospital in central London. The royal baby's name has not yet been released.
The Duchess of Cambridge delivered her second child several days late at 8.34am on Saturday and was in labour for just over two and a half hours, with Prince William present for the birth, in the Lindo Wing of St. Mary's Hospital – the same hospital where Princes William, Harry and George were also born.
She weighed 8lb 3oz and is the fourth in line to the throne, behind grandfather Prince Charles, father Prince William, and brother Prince George.
It is not yet known how long mother and baby will remain at St Mary's, but she and Prince George spent just one day there after his birth.
Buckingham Palace is expected to formally announce the birth with a bulletin displayed on an easel outside Buckingham Palace.
The Queen, Duke of Edinburgh, Prince of Wales, Duchess of Cornwall and the baby's uncle Prince Harry had been informed and are "delighted" with the news, the palace said.
This birth knocks Prince Harry, her uncle, back into fifth as heir to the throne and her weight makes her lighter at birth than her brother George, who weighed 8 pounds and 6 ounces (3.80 kg) at birth.
Crowds of royalists and the world's media had gathered outside the Paddington hospital in anticipation of the royal baby.
The Royal Parks have been decked in flags to welcome the new born royal and Union Jacks have been placed along The Mall.
Rumours had been circulating that the Duchess was close to birth and after speculation on the baby's sex and date of birth, bookmakers suspended betting on when the baby would be born after a flurry of bets on Friday morning.